Mostly I find it useless to argue with Teabaggers. As Charlie Chan once said: "Is like train with no wheels, get nowhere fast." But a few years ago I did convince one of them that Utah should not pass a law banning same sex marriage. My personal attitude about gay marriage went from hell no, to well maybe..., to why not, to hell yes. Sometimes it takes me a while to get on the right side of an issue, but I usually get there sooner or later. When the Mormon Church got involved with Prop 8, it irritated me enough to resign from the church.
What I did was to turn their own heavy weapons against him, the Constitution and the Bible. The equal protection clause of the 14th Amendment clearly states that all laws have to apply equally to everyone. A law cannot say that one group of people can get married and another group can't. Do you believe in the Constitution or not? Well... the Bible still says it's wrong. Yes it does. It also says that disrespectful children should be put to death. Do you believe that? Well, no... Why not, it's the word of God isn't it. Well, you can't go by everything you read in the Bible. Ok, I guess gays should be allowed to get married. But I still don't like it. That's ok, you aren't required to like it.