I remember getting into towering arguments with Freddy. Inevitably, I would lose my cool and send Freddy to hell. In the end though, I would get mad at myself because I know better than to argue with a crazy person. You can't ever win.
The way I see it, you have 4 options:
Kill the crazy person before their Crazy invades your brain. Granted, the police don't like this so you will get into trouble. Other than self-defense, I don't recommend this option.
This is guaranteed to fail. You may beat them senseless with your brilliant logic, but their Crazy will always win. Don't argue with a crazy person. It wastes your time and riles them up. The last thing anyone needs is for crazy people to go crazy.
3. Be crazier.
I find that this works spectacularly well. I quickly agree with the crazy person...then escalate. Think of it as protecting your sanity by wrapping it in the armor of insanity. For example, if a crazy person starts talking about alien abductions, I scream about hollow earth, crop circles, the Loch Ness monster and my political support for that great American - Bigfoot!
Just run for your life. Get away as fast as you can and hopefully The Crazy didn't catch.
Don't get caught in an argument with a crazy person. It's a complete waste of time. I can't tell you how often I have some nutcase who wants to argue with me. Just ignore them, or go crazier to escape with your sanity.