I'm under no obligation to prove anything. In this life, God isn't on trial. We are. And I could go into how I know but that would be the classic case of throwing pearls before swine.
Of course you are not, until you keep your beliefs to yourself. But then you are telling me homosexual acts are wrong. Even then I still could live with that, until you come out and say society should not let them get married. At this point you are under the obligation to prove first there is a god, and that he has said so.
However if you live and let live, I could care less if you believe in bigfoot or god or whatever else you like. It's your first amendment right.
"Fire cannot kill a dragon." -Daenerys Targaryen, Game of Thrones
