You know you're a racist...
You know you're a racist when you think the phrase "black lives matter" requires a rebuttal.
Whoever crafted that phrase came up with a clever trap for racists. It's a logic puzzle they can't solve but can't stop themselves from trying: Black lives are contained within the set of all lives. Only when you see a different Venn diagram do you feel compelled to answer.
Black lives matter. That's all that was ever required.