It seems to me like the more intellectually honest characterization of things like hiring quotas and admissions quotas is "discrimination in the interest of the good" or "compensatory discrimination" rather than "this isn't discrimination". It's not a little-known practice and it doesn't negatively affect only white men (it also negatively affects East Asian men, for instance).

If you think those hiring practices are justified against a backdrop of ongoing white supremacy, patriarchy, etc., say that. If you think they're only a small adjustment in the big picture in a world where tacit norms of credibility, transgenerational wealth, and interpersonal connections still overwhelmingly favor white men, say that. But when someone says "hiring practices actively try to tell people apart by race and ethnicity in a way that disfavors my odds" and you reply amounts "nuh-uh, and you can't say that!", you frankly weaken the left, because you aren't addressing the real contention and you look to outsiders like you are denying an obvious fact.