which lead me to believe the joke part was unrelated to anal bleaching and the intended joke was Ha, aren’t white supremesists stupid and annoying

You got it backwards: I was joking about anal bleaching and serious about white supremacists being stupid and annoying, though my way of expressing the latter was intentionally flippant for levity 😁

The topic of white supremacy in and of itself is completely unrelated and shoehorned into the conversation though.

That’s part of the joke: going off on a true but completely unrelated tangent that supposes the first part of the comment to be true. Just committing to/building on the bit.

Part of the humor was in the going back and forth between pretending that I think that the two things are related and making clear that I don’t.

I admit that it’s a bit complex as far as joke structure goes, but most of the other people reading seems to have either gotten it or just ignored it and moved on rather than lecture me on having fun wrong.