Religion is more of an idea, less something you can prove and asking someone to prove that shows how little you understand about religion.
Also, it's silly to pretend that your belief or idea can be the only correct one. Slightly off topic, but back in college I had a girl friend call me on the phone crying because she honestly believed her roommate was going to Hell. She knew this because the girl was Buddhist or some Asian religion (it's been too long and I care too little) and my then girlfriend knew that she was wrong. When I asked her how she knew she went into a rant about she knew God existed because she felt him, saw him perform miracles, etc.
I thought for a second, and then asked what if she knew the same thing? Or rather, what if someone said to her those same things to her about another god? Which one is right?
In the end, it doesn't matter who is right. They believe what they believe. Them believe in a different god doesn't change what you believe and as long as they're still a good person, then isn't it alright?
So back on topic, kind of, it doesn't matter if we can't prove to you explicitly that God exists. The simple fact is we can't and you probably know that. What matters is what each of believe, whether that's belief in the one true God or no god at all, and working towards being a good person.
Now all that said, why does it matter to you so much that we prove God exists? To everyone else getting upset, don't worry about it so much. What does it matter if he doesn't believe in God because he can't explicitely prove he exists? It's his choice and it doesn't affect your beliefs one bit. I understand religion is a touchy subject but please don't let the little things bother you so much. You have your faith and a simple forum thread shouldn't shake that. 
