> As an example, a whole bunch of people, for some reason, took "Black Lives Matter" to mean "Only Black Lives Matter", as if that was said or as if that was the point.

That was never my issue, or the issue of anyone I encountered. My issue (and those other people's issue) was the implicit bad-faith assumption that we didn't already think black lives mattered, and needed to be scolded about it. Such rhetoric is needlessly divisive and should be avoided.