These people are delusional.
I went through this at Thanksgiving a few years ago with our oldest male relative, when I mentioned Communists in our unions. He sneered at the top of his voice that we defeated communism long ago! Oh. Kaaaay. I quietly stated that we defeated the Soviets, but not communism, and got up and left the room. It just wasn't worth a prolonged argument in front of the rest of the family.