Cursed Boomer Images - Nice. Real Nice

I mean it's not wrong

Context is the difference. "Black lives matter" isn't an assertion that only black lives matter, it's an assertion that black lives do matter. It's diluting someone's assertion that their life is significant. Like if you beg someone holding a gun to your head not to kill you and he comes back with, "Wow, wouldn't you really not want me to kill anybody?"