I'm trying to say that when I say "I oppose racism", intending to signal "I oppose people beating up minorities", and people misunderstand badly enough that they think I mean "I oppose IQ-by-race studies", it disturbs me.

That's because most people who say "I oppose racism" mean the latter, and no one except you means the former. That's largely because most people oppose beating people up for no good reason and thus they don't feel the need to constantly go about saying so.