There's a pretty simple test, IMO
Ask a person "is bombing a school filled with children okay as long as the end goal brings about the end of the world?"
If they answer "yes" then just immediately drop them into a meat grinder and use the remains for fertilizer.
Maybe it's my cynical side, but I genuinely don't think people like that can be fixed, so while it might be considered "cruel" it's better to just put them out of everyone's (including their own) misery, a "nuthouse" just gives them a place to congregate and keep trying to spread their hate.
I've been managing to drag some of them further left, I think, through conversation about things.
A few are 100% on board with a union as long as I keep calling it "collective bargaining" and don't use the scary U word.
A few are on board with most social safety nets, especially when they find out Healthcare would cost less than it currently costs them in taxes alone, let alone not having to pay for insurance anymore, but the second you call it socialism or use any sort of word like "welfare" then they panic.
Individually I think I'm breaking some of them, but collectively they're fucking idiots.