You don't have to accept this. You can set boundaries, like, "I'm willing to come visit for Xmas only if we don't talk politics." And be ready to enforce it. If they don't agree, well, win-win! You get to stay home and enjoy yourself. If they do agree, then break that boundary, be willing to pack it all up and leave RIGHT then and there.

You don't have to be treated like this. If they want your company, they've got to show you some damn respect.