"You're 100 Percent Correct"
It doesn't matter what you're arguing about—he just wants to be right. This is his weakness; you can use it like judo, turning his own momentum against him. Saying two little words, "You're right," is the verbal equivalent of darting a raging elephant with animal tranquilizers. It gives him what he wants, reducing tensions and leaving the way open for you to get what you want. Try it: "You're right, but I still want to go to the party." Meet every protest and argument he makes, no matter how ridiculously false, with the observation that he is absolutely correct...but you still want what you want. In boxing this is called rope-a-dope, and even if you don't know what the rope part means, the dope part sounds pretty applicable. This is called win-win—except you did and he didn't.