Yeah, of course you'd quote MLK and not Sakai or Fanon or Sankara or Bishop or Du Bois or Newton or bell hooks or Barbara Smith or Malcolm X or literally anyone but the most absolutely sanitized of Black activists or politicians... To quote MLK, not just in general but especially to quote the literal only speech of MLK that you ever hear about in school, is rhetorically equivalent to saying "but I have a Black friend!" — it's an extremely tired trope just like this whole Reddit Speech thing you've got going on that shows zero comprehension of the issue and zero reflection or self-awareness on your part. Especially when you focus so much on definitions and seem to define race purely by skin color, rather than understanding racial issues through dynamics and relationships. This is the exact type of thing OP is talking about.

It is not at all unreasonable to understand that when there are systemic differences in housing and employment and generational wealth and health outcomes and so on and so on and so on, that someone who didn't get to experience the shorter end of the stick is going to have the lack of those experiences get reflected in sy beliefs, attitudes, and behaviors, just like any other facet of lived experience. Assuming that white people generally aren't going to ever fully "get" racial issues, and will therefore have an incomplete understanding of all other issues with which racism intersects; and moreover assuming that when white people benefit from the oppression of racial minorities which they get to live shielded from, that they broadly get to live in enough comfort that they won't be easily driven to genuinely radical thinking... That's not being a racist, really, that's just like assuming that a medieval peasant isn't going to ever fully "get" microbiology when microscopes haven't even been invented yet.

When you pull the old device of "oh so it's OK for them to do this but when I do this to them then it's a problem" it's denying that differences do exist in the lived experiences of people of different racial and ethnic categories. The following is what it means when someone is judged by the content of sy character rather than the color of sy skin: that everyone has the potential to understand others or to achieve great things, when the systems of society that blind some to the suffering of others, or keep those others down, no longer exist. "Content of sy character" should not be taken to mean that race is a non-factor in someone's lived experience.