Specifically, can white supremacy be considered a creed as it is a widely held philosophical belief?
I, semi-contrarily, speculate that the answer is "yes", as long as we understand your question to be about religion, since that is what is legally relevant in terms of discrimination law. The EEOC "answers" the question in 29 CFR 1605.1, saying
In most cases whether or not a practice or belief is religious is not at issue. However, in those cases in which the issue does exist, the Commission will define religious practices to include moral or ethical beliefs as to what is right and wrong which are sincerely held with the strength of traditional religious views. This standard was developed in United States v. Seeger, 380 U.S. 163 (1965) and Welsh v. United States, 398 U.S. 333 (1970). The Commission has consistently applied this standard in its decisions. The fact that no religious group espouses such beliefs or the fact that the religious group to which the individual professes to belong may not accept such belief will not determine whether the belief is a religious belief of the employee or prospective employee. The phrase “religious practice” as used in these Guidelines includes both religious observances and practices, as stated in section 701(j), 42 U.S.C. 2000e(j).
The question then is what the court said in those cases that could possibly be construed as a definition of "religion". The case of Seeger, which pertains to conscientious objector status and the draft, held the following relevant points:
The test of religious belief within the meaning of the exemption in §6(j) is whether it is a sincere and meaningful belief occupying in the life of its possessor a place parallel to that filled by the God of those admittedly qualified for the exemption.
Observe that the court does not generally define religion here, rather, it strives to interpret a clause in the Universal Military Training and Service Act, 50 U.S.C.App. § 456(j), which denies that there is a requirement to serve in the military on any person "who, by reason of religious training and belief, is conscientiously opposed to participation in war in any form". The statutes more specifically says:
As used in this subsection, the term "religious training and belief" does not include essentially political, sociological, or philosophical views, or a merely personal moral code.
Congress, then, also did not attempt to define "religion", rather it used that term to refer to certain undefined beliefs (it them becomes the court's job to define the term, relative to the act).
Seeger also holds that
Local boards and courts are to decide whether the objector's beliefs are sincerely held and whether they are, in his own scheme of things, religious; they are not to require proof of the religious doctrines, nor are they to reject beliefs because they are not comprehensible.
This means that, w.r.t. the draft and the religious exemption, the basis for deciding is whether the beliefs are sincere, and whether they are in the subjects "scheme of thing" religious. I also bold the clause about not requiring proof of doctrine, since that will be an issue below.
In Welsh it was held that:
Section 6(j) contravenes the Establishment Clause of the First Amendment by exempting those whose conscientious objection claims are founded on a theistic belief, while not exempting those whose claims are based on a secular belief. To comport with that clause, an exemption must be "neutral" and include those whose belief emanates from a purely moral, ethical, or philosophical source.
The significance of this is that the conscientious objector clause flouts the Establishment Clause by specifically giving preferential treatment to beliefs founded on a theistic belief, but not a non-theistic belief. Thus, to be consistent with the Establishment Clause, the term "religious" must be interpreted in a way that does not favor theistic vs. non-theistic beliefs.
In both cases, defendants were raised religiously but were not members of a church with an officially pacifist doctrine. Quoting Welsh, the defendants
neither could definitely affirm or deny that he believed in a "Supreme Being," both stating that they preferred to leave the question open.
affirmed on those applications that they held deep conscientious scruples against taking part in wars where people were killed. Both strongly believed that killing in war was wrong, unethical, and immoral, and their consciences forbade them to take part in such an evil practice.
Thus, "firm belief" is the interpretation of "religious belief" w.r.t. the draft, and is relied on by the EEOC in their definition of religion.
The question of whether white supremacism could be deemed a religion, w.r.t. discrimination laws, came up (and was basically avoided) in Swartentruber v. Gunite. The issue there was that the complainant had Klan tatoos, and his employer told him to cover them up. He sued the company (Gunite) for religious discrimination, to no avail. As the court summarized, he would have to show that
(1) he has a sincere religious belief, observance or practice that conflicts with an employment requirement; (2) he informed his employer of the conflict; and (3) the religious practice was the basis for the adverse employment decision.
His case failed for a number of reasons, but the crux of his argument was that
the "Firey Cross" tattooed on his arm is one of that church's seven sacred symbols
(he reports that he is "a member of the Church of the American Knights of the Ku Klux Klan, a religious organization"). However,
Mr. Swartzentruber does not present admissible evidence, or even contend without evidence, that being required to cover up his tattoo at work conflicts with his religious beliefs
This appears to be at odds with Seeger above, because one is not required to prove that ones religion has a particular doctrine. Since Swartentruber represented himself, this could well mean nothing more than that he failed to make an appropriate assertion about his firmly held beliefs (since one is not required to show that their church has a specific doctrine).
The basic reason why Swartzentruber's case failed was, simply, that his employer did in fact offer him a reasonable accommodation. Firing a person, on the other hand, is not a reasonable accommodation. Following the logic of Welsh and Seeger and being mindful of the Establishment Clause, one might well expect that an ideological firing would be a violation of the religious discrimination part of the Civil Rights Act. The belief in question would have to be firmly held, but need not be theistic. Since the matter has not been decided by SCOTUS, we cannot know how they would rule if the matter came before them. There is, at least, a clear precedential path where white supremacism could be held to be a religion.
In addition, if the incident took place in Seattle, the firing would be illegal because city ordinances prohibit discrimination based on political ideology.
I am assuming that you mean "creed" in the sense of discrimination under federal civil rights laws in the United States.
The answer is basically "no", subject to a narrow exception that is more conjectural than real at this point, which is explored below. When push comes to shove, it is hard to imagine a fact pattern where this exception could possible apply to protect a white supremacist employee.
A non-religious philosophical belief or ideology is not protected as a "creed" by civil rights laws.
Indeed, an employee or prospective employee's commitment to white supremacy can be a valid reason to discriminate in employment because if the employee acts, either consciously or unconsciously upon those beliefs, the employer is exposed to legal liability for discrimination based upon race and/or national origin and/or religion, so the employer is justified in avoiding that liability.
Also, ethical rules for judges prohibiting them from espousing discriminatory views or from affiliating with discriminatory organizations (which are present in almost every state), and similar rules for lawyers (which are present in many states, but do not prohibit representation of discriminatory organizations as clients), have generally been upheld as valid.
What If One Claims To Be Part Of A White Supremacist Religion?
The situation becomes muddier, however, when an employee claims that the employee is a member of a theistic religion in which they have a sincere belief which has white supremacy as on of its ideologies.
Practical Difficulties Involved In Making This Claim
Historically, there were relatively mainstream religious bodies that adhered to white supremacist views (e.g. Southern Baptists prior to 1995 and the Church of Latter Day Saints prior to 1978). But, that isn't the case now, undermining this argument for white supremacists who are members of mainstream Christian denominations (which many are by virtue of inertia, without ever having given it much thought).
Given that many white supremacists in the United States self-identify a Christian (and usually as Evangelical Protestant Christian in substance if not in the exact wording used), it is challenging, although not necessarily impossible, for them to make such a claim.
For example, both the KKK and the historical Nazi party, were explicitly Christian organizations. Indeed, the Ku Klux Klan was expressly both anti-Jewish and anti-Roman Catholic (and obviously, didn't have a warm place in its heart for adherents of historically African-American denominations of Protestant Christianity either). Most contemporary white supremacist groups in the U.S. are also explicitly anti-Muslim and are inclined to be anti-Hindu if they ever think about that religion which is mostly "not on their radar screen."
Most U.S. Christian denominations (really, almost all of them) have expressly disavowed white supremacy as a matter of formal denominational policy (some more recently than others), and I am not aware of any that formally adhere to a discriminatory policy (although I don't claim to be omniscient), so claiming an affiliation with any of these denominations would not suffice.
Also, an individual who had been, for example, a member of a Southern Baptist Convention church (which formally disavowed most of its white supremacist doctrines 22 years ago in 1995) all of his life and claimed to have secretly joined some splinter denomination that espouses white supremacy shortly before the employment issue came up, might have difficulty proving "sincere" religious beliefs of this type as opposed to a "sham" religious affiliation in a court. This would be particularly difficult if the alleged splinter denomination is tiny with only a handful of members, and hasn't been around for very long.
What If A Claim Is Squarely Presented?
This said, there is not a lot of clear case law governing whether there is a freedom of religion exception to anti-discrimination laws based upon an alleged theistic religious mandate to discriminate, if the conflict did clearly come up in a case.
The cutting edge cases on this issue involve gay rights, rather than race. The basic line that seems to be emerging in the case law is that a religious exception can protect you from liability under anti-discrimination laws in a religious entity or a religious context, but not in a secular one.
But, even in a religious entity or a religious context, the stance that courts would take would be to refrain from enforcing anti-discrimination laws against the employer, not to protect a white supremacist employee for discrimination.
In a secular context, a racist religious belief system is not going to protect you from liability under anti-discrimination laws. Furthermore, because of this fact, it is not going prevent an employer from using the likelihood that you will violate anti-discrimination laws to refrain from hiring you, or to fire you, or to demote you, or fail to promote you.