It’s against the law and whites could do a class action law suit.
A defense contractor I’ve worked for justified all the Employee Resource Groups for women, blacks, hispanics, gays, etc. and prohibiting it for whites as a step to remedy prior discrimination - but said it wasn’t discrimination as long as whites could join one of the existing minority group ERGs as an “ally”.
In short, discriminating against whites wasn’t seen as discrimination, or rather, rectifying past wrongs.
The problem is that discriminating against the majority is a bad proposition in a democracy. Penalizing the largest taxpayers is simply stupid.