While it is not wise to end familial or friendship relationships willy-nilly, there does come a point where you have to just say, "I don't know what to say to you anymore, but maybe we just need to stop talking about politics".
At that point, if the other person is persistent in advocating what I consider utter hogwash, stuff without any factual merit, I can just stop listening to them. Maybe call the funny-farm wagon.
Valujet (Randy, former moderator here) was a lifelong friend of mine, my brother from another mother. We had a huge falling-out back in the early 2010s, and didn't speak to each other for a couple years. Thankfully, we made amends and were back to being snide goofballs by the time he passed away a couple years ago.