which in America means black people specifically.

Um, nope it doesn't. For example, a black person who lives in an affluent, low-crime area and adopts high-status signifiers such as wearing a suit-and-tie is extremely unlikely to be affected by police brutality. This is not to say that being black isn't highly correlated with being victimized in this way, but the whole point of the previous comment is that correlation is not certainty, and there's nothing 'specific' about it.

This is also why your criticism of the "All Lives Matter!" meme is rather off track - the whole notion that such things can "derail the discussion" is unproven and quite possibly meaningless. In all probability, it's little more than what we here at Less Wrong would call a cached thought, or even more pointedly a semantic stopsign, or thought-terminating cliché.