Does God exist? Should America allow “gay marriage"? Those are 2 separate questions. There are many books that “prove” that god does not exist. There are many books that “prove” that god exists. People have been discussing it and debating it for centuries. It is highly unlikely that man will ever come to an agreement. Thankfully, at least in America, one is not required to believe that God exists.
I thought that I’d chime in and answers Avatar’s question from my perspective. Some people have read apologetic books and, after having read those books, come to the conclusion that God exists. Some people read books and came to the opposite conclusion. Some people base their faith on nothing more that wishful thinking. Some believe that God exists because their fathers and mothers said that God exists (the bandwagon phenomenon). Some believe that God exists because they just “feel” that God exists. Some people claim to have had “religious” experiences. There are many reasons why people believe and reasons why people don’t believe.