Why not? Should “they” be held to a different standard? It’s ok to call a bunch of white kids monkeys, which I do often, but not ok to call a kid who is black a monkey because there are issues there? Hmmm. Maybe those who are offended need to get over it?
Maybe you should just accept reality.
Calling someone black a monkey a chimp or a gorilla makes you sound racist while calling someone white a chimp or gorilla isn’t.
That is just how it is.