People aren't mad that black people had the nerve to proclaim their lives matter. Most I know wouldn't have said otherwise. They simply point out the problem with the usual leftwing duplicity behind it all. That is, insisting they aren't saying only black lives matter, and then watching them suggest anyone who says all lives matter is a racist.
The Left's favorite tactic of denying having stated the implicit truth they just used to separate the sheep from the greatest of all time, is the problem. And pardon me for noticing, but the only one who seems mad about any of this is Ms. Harris.