If theists would stop claiming that there was a god, then Atheists wouldn't exist - we would all just "be". We wouldn't have to even bring this god business up at all if you guys didn't claim so loudly that it was THE TRUTH!!! GOD SAYS SO!!!
The only reason that it seems like atheists are proselytizing is because for a large majority of human history, religious people have made baseless claims and created rules and laws to make society fit those claims. You've (as followers of any major religion) imposed your views on people from all walks of life simply because you feel like you know more than everyone else. That's wrong. It's only recently that we've had the collective balls to stand up against that. The social stigmas that have been associated with religious belief have caused countless amounts of grief simply because religion imposes itself on those around it by "spreading the gospel", for example. All we are doing is refuting the authority of these religious claims based on what is actually observable reality.
We aren't trying to take away your right to practice your religion. We are taking away your right to impose that belief system on people who don't want it. That's it. And it's not because we are atheists. It's because doing so is wrong.
Now, personally, if you make a claim on the internet that isn't supported factually, you shouldn't be surprised that people refute that claim. If you claim doesn't stand up, then what does say about the claim? I think the Bible says something about this as well...
This is not an emotional thing for us (some of us). You guys (theists) believe in something that can't be supported factually.
You want to know a big secret? There's nothing wrong with that. Enjoy whatever brings you fulfillment. Who cares if I don't believe in it? Your faith shouldn't be affected by my lack of faith. Have you ever debated with Greek Polytheist? You think their claims are bogus, don't you? Do give their god(s) any credence whatsoever? What you do at that point is what we do all the time. There is no difference.