some law students from Whittier Law School (the name is real, i am not making a pun) got all sad that a law professor wore a Black Lives Matter t-shirt on campus and they had to write a letter. The professor responded.
Both the initial letter and the response are in the link, please read them.
If nothing else, at least understand this simple fact: Black Lives Matter doesn't exclude white people or any other group. There isn't a silent "only", there is a silent "too". In any other situation where such phrasing is used, there is a "too", not an "only", implicit. "We sell lottery tickets" a shop owner might put in his window. That doesn't mean he only sells lottery tickets. "Hugh Jackman enjoys pizza" a tabloid might try to pass off as news, that doesn't means Wolverine's diet is only made up of pizza because he doesn't enjoy anything else.