I think it really is just the simpler explanation, they have decided they hate anybody left of them, and defeating them is the cause which much be won at all costs.

I have plenty of these folks in my family. Perfectly nice people otherwise. But they have this huge conception of the evil liberals and all the bad things they must do. They really do think liberals are commies, for example. Like actually believe that. Never mind that you could probably fit all the communists in the US in a single stadium, but whatever. When I try to engage in a conversation about actual issues, they refuse to engage, just devolving right back into plain old identity politics.

Makes me kind of sad in a way. We could be having much more interesting debates about how to solve the real world problems we face, but instead the argument is about whether or not the problems even exist.