No, he doesn't have to prove it to a non-believer, but he then shouldn't expect us to respect his belief. Respect him but not his belief.
If a Hindu can not eat beef (or meat, in some cases) or a Muslim can not eat pork I would not shove BBQ ribs and a Big Mac down both their throats because I do not agree with their "belief" that pigs are dirty or that cows are sacred. Nor would I ridicule him for believing in those things. But if he were to tell me to stop eating meat in general or eating cows or pigs and calls me a savage for eating meat, I'd be pretty pissed. If he told me my belief that "there is no God" was going to get me into hell, again, I'd be pissed.
Explain to me how you can respect a person while not respecting his beliefs. Please don't tell me "respect" is analogous to "agreeing with." I see it as a more like "understanding and being tolerant of."
You also cannot prove that the following do not exist:
Dragons
Unicorns
Flying monkeys
the Omaticaya people of Pandora
The Flying Spaghetti Monster
A neon pink spotted three headed magical lion called Dave The Magic Lion.
a 50 foot spider with 100 legs that lives under the sea and only eats Kraft Macaroni and Cheese, which is hand-delivered in waterproof boxes by Dave The Magic Lion on a weekly basis.
So, do you also believe in those? What would you think if I told you that Dave the Magic Lion was the real jesus, muhammad, buddha and moses because he was a shapeshifter?
Listen up. THE BURDEN OF PROOF IS ON THE CLAIMANT.
I can see how this applies to someone that preaches about God out in the public. But what about the person that practices in the privacy of his home with his family? He doesn't give a shit that you're atheist and that some members on this board dunno wtf to think about religion. He sits there and prays, meditates, reads holy books, and feels that it improves his life. You have no dirt on him. To say he's religious, and therefore "stupid" or "uneducated" or whatever adjectives you throw around to describe Believers is a result of your intolerance. He has nothing to prove to you unless he decides to debate with you.
Even if you theorize that all this couldn't have just come from nothing, that doesn't mean it came from God. All it says is that maybe it didn't come from nothing. Fine. You can theorize it came from another universe or that this nothing as we know it is really something on a quantum level. Fine. That still shouldn't point at anything like anyone's conception of a god. It shouldn't bring any comfort, promise of an afterlife, or meaning to you if you believe in a process you don't understand. There's no reason to theorize that it needs your prayers or elaborate ceremonies or anything from you. All you can say is that this must have come from somewhere or out of something, I don't know what. No need for beliefs or names or attributes or stories with moral endings. In other words, extreme atheism is warranted.
Have you ever thought that "God" is merely a name people have given to something that they don't truly understand? Ok, that seems a bit obvious, but do you think that after all the science and religion bullshit has surpassed, we still haven't gotten it right? About what started this all?
I spent a lot of time in my physics class wondering how all this shit came into harmony. "Shit" like the laws of physics on Earth and in the Universe, and beyond. There is stuff in physics so far beyond the average person's grasp, it's stupid. What if everything came from one particle? Or one theory? You know how many theories there are in physics and astronomy. What if everything we have is a misnomer? To say "science" would be so broad, how could atheists possibly say they were right? And what if religious people merely personified a theory or particle they knew nothing about? Either way, it's ignorant, but neither side is right in this scenario. Which means all this bickering is over something that, right now, can only seem to be answered once we die.