This should not be controversial, but some people read too much into this sentence. If people read it as “only black lives matter”, then they are reading it wrong. Read it literally. No one should dispute that all lives matter. The problem is that police, and some civilians, treat black lives as if they don’t matter.
If Chinese Communist party officials are abusing, brainwashing and sometimes killing Uighurs in Eastern China, it’s appropriate to say “Uighur lives matter!