Let me try to find a legal question here.
The SE main TOS page states that
Stack Overflow reserves the right to refuse, suspend or terminate your
access to the public Network if it determines, in its sole discretion,
that you have in any way violated these Public Network Terms or are
otherwise ineligible to access or use the Network or Services.
The question of whether SE will get sued over this policy is therefore "No", they have complete discretion to kick you off.
Still, maybe there is some question as to what the word "illegal" means. The popular meaning of illegal is "prohibited by criminal law", but the broader meaning assumed on Law SE is something like "may reasonably be negatively sanctioned if brought to court", and includes crimes, torts, breaches of contract, administrative fines, judicial injunctions and so on.
Presumably the real intent is to prohibit uses which encourage actions that stand a reasonable chance of being found to be illegal, were the matter to be brought to court (everything "may or may not be legal"). Without calling into question the logic of such a principle in the first place, and unless you refine the principle to narrowly mean "criminally prohibited", then this means "is it illegal to run Mac OS on non-apple hardware". It sort of looks like it is a violation of the EULA for the operating system, which makes it copyright infringement to do so (and illegal in virtually every nation, except Iran and Eritrea).
It is entirely unclear what the prohibition against "illegal use" is supposed to refer to. It is not universally illegal to advocate certain (unnamed) political positions, but it is in some countries. Hate speech is legal in the US, and illegal in other countries. It may be illegal to describe how to violate a software EULA in some country, though it is not, in the US.
