Interesting piece. I get a little tired of being told what I can and cannot say in this new racist/anti-racist dichotomous world I find myself in. That said, I accept your premise. But, if I should not say "not all White people", then why is it OK for you to say "all White people"? By "you" I refer largely to Black authors, many published on this site - see Marley K.
I will say this, not to contradict you, but because there is a ring of truth to it. Not all White men are racist, misogynist, homophobic bigots, but all racist, misogynist, homophobic bigots are White men. Can I say that?