It’s partly an emotional reaction. When we are joking about genociding a group or sterilizing them, I have a visceral reaction like I’m reading a fascist website. The emotional side of me just doesn’t understand why we even want to talk like that. It’s horrific.

It’s also logical in part - engaging in that sort of speech implies that such things are acceptable or things to be joked about. That sort of suffering deserves respect from leftists. Would you joke about white genocide with a holocaust survivor?

Further it implies races are things to be divided up and are real on some level.

Personally I’m gay. I don’t engage in hating straight people.

I focus my hatred on bigots. I focus my hatred on conservatives.

Ultimately, I agree the harm is not that great. I’m not reporting comments or asking for that speech to be banned. But it’s not a viewpoint I have seen expressed before and I felt the need to share it.