The theory behind the objection seems to be that black people must help white people fix problems that white people experience before we can even talk about the problems that black people experience. That seems crazy to me.
Even if the US hadn't uniquely maltreated black people for centuries, black people are just 12% of the population. Why shouldn't they be able to call attention to the problems they experience without white people saying, "But what about meeeeeeee?!?"
Yes, there are a lot of things wrong that we should fix. But when somebody tries to discuss problem A and somebody else immediately leaps in to say, "Why don't you care about B?" I often suspect that the point is not to fix problem B, it's to stop the discussion of problem A.