Just because they asked him if black lives matter doesn't mean they're a part of the BLM movement. They were probably just some dumb, violent kids looking for trouble. But of course people will try to pin this down as another piece of "evidence" that BLM is racist, while ignoring the fact that Black Lives Matter can be claimed by anyone, anywhere at anytime.
Any real, respected person in the BLM movement would never condone attacking someone off the random like that.

That's probably why they aren't considering it a hate crime. Hope he gets justice against those kids of course, but this has absolutely nothing to do with the BLM movement.