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What it really boils down to is this: "As a beneficiary of privilege, it makes me uncomfortable when people point out that racism and sexism exist. I can't say they're factually wrong, so I'll talk about the tone instead. If they would just stop being so uppity and find a way to solve the problems of racism and sexism that do not make white men uncomfortable or take any action, everything would be fine. But they haven't, and it's their fault."
Does that seem like a "concrete, non-racist criticism" to you? Sorry if I can't magically remove race as a factor in the tone argument, but reality interferes. The tone argument is made almost exclusively by whites. You can call it "racist", but you can't change the fact. Calling it racist is a cop-out, a convenient dismissal of a valid and problematic point.