As George White says, it's hard to prove a negative, but in this instance, there's quite a bit of evidence supporting you. First, the ABA has standards for legal commentators but they are very weak. They say pretty much what you would expect, and, they are non-binding: they explicitly say they "not intended" to provide grounds for "professional discipline." Second, there are articles by lawyers indicating there are no state bar standards. Taken together, the weak ABA standards and the articles should give you enough evidence to prove your case in the "court of buddy opinion."
The ABA rules on legal commentators were issued in 2013 as part of a Fair Trial and Public Discourse Black Letter. The letter covered public comments on cases by lawyers involved in the case, lawyers not involved (ie, commentators) and judicial and judicial employees.
According to the ABA, the standards are:
intended to provide a guide to best practices for lawyers who provide public commentary or consult on criminal cases in which they are not personally involved; (Standard 8-1.1(a)(ii))
To explain what it meant by a "guide to best practices," the ABA included the following caveat about the applicability of the standards:
While these Standards are intended to provide a basis for the formulation of internal guidelines within lawyers’ offices...they are not intended to serve as the basis in and of themselves for the imposition of professional discipline...(Standard 8-1.1(c))
In other words, the ABA's rules truly are just a guide to best practices.
As for the guidance itself, it does not come close to requiring "due-diligence."
A lawyer who is serving as a legal commentator should strive to ensure that the lawyer’s commentary enhances the public’s understanding of the criminal matter and of the criminal justice system generally, promotes respect for the judicial system, and does not materially prejudice the fair administration of justice, in the particular case or in general. To that end, a legal commentator should:
(i) Have an understanding of the law and facts of the matter so as to be competent to serve as a commentator;
(ii) Refrain from providing commentary designed to sensationalize a criminal matter; and...
It may be that some states provide more stringent restrictions, but a quick search suggests they don't. Otherwise, there would not be a law review article arguing "The Legal Profession Must Broaden Ethical Standards for Legal Commentators," or an ABA Journal article (from this June) giving advice on becoming a legal commentator without mentioning state bar restrictions.
I'm sure if you look, you can find more evidence.