BLM is not trademarked (people have tried and failed though!) so it's not a brand. It's three letters so it doesn't qualify as a logo. If it were consistently stylized then maybe it could be considered a logo. But there's not consistency in the stylization, only thing that's consistent is it's the same three letters from the alphabet in the same order.
LOL <- do you think that's a logo too? If so then, LOL at your silly rationalization. Oh noes, someone might sue me for infringing on the "LOL" brand/logo!