Really quick this time, but to put up-front something I mentioned in a few comments:
I am trying to talk about actions and ideas, not about people, when I'm talking about racism. Here are two reasons why.
[When anti-racism activists are educating/arguing the anti-racist position,] the purpose is to present anti-racist ideas to people as clearly and convincingly as possible. It has to be done smoothly, in such a way that it slips past defenses to present a point of view that people may not have thought of before, such that their first reaction is “Oh, interesting—I never thought of that before!” not, “Shut up! I am not!” The former lets the person think the idea over and decide whether or not s/he agrees with it—the latter cuts off that possibility before the conversation’s started.
Racism, homophobia, and all the other sins are not adjectives: they are verbs. Each individual action counts. It's not whether you are racist, it's that you just said something racist that matters. So suck it up, consider the action, apologize, and don't do it again.
I see these as two sides of the same coin. And I'd take it as a courtesy if people would consider this when commenting in my posts.