I would not say that an atheist believes staunchly there is no god. There is a broad spectrum of atheists. People confuse this all the time. Atheism is the lack of a belief in a god. It's not the belief that there isn't. There's no believing associated. I don't see evidence for one, but I am completely open to changing my mind if I were to come across such evidence.
I think theists think most atheists are more like
when really most of us are like
and some are a little bit
This is the difference. If someone is Jewish, or a Muslim, or a Christian, there are sets of beliefs that are perfectly rational to assume that that person holds as a result of their religion. If someone is a Christian it's probably safe to assume they believe in heaven and hell, or that Jesus is the son of God. To know that someone is an atheist means that you know almost nothing about that person or their personal beliefs. You could assume they probably believe the theory of evolution, or that they're probably not members of the Tea Party, but those beliefs aren't a result of someone's atheism.
What I'm trying to say is that atheism is not believing in something. It's not believing in nothing. No rational atheist is opposed to believing in a god. If presented with such evidence, most regular atheists would jump the fence. We all know atheists that shove it down everyone's throats just like we all know religious people that shove it down people's throats. If Jesus shows up in Times Square tomorrow, and he's healing the sick and turning water into wine, sign me up right now. I'm all in. I'm not saying that's the proof I need, but there are demonstrations that could convince most atheists. Atheism is just the position of not being convinced in the existence of a higher power. There's no sort of doctrine within atheism at all. All we have in common really is a failure to be convinced. And we could be wrong.
I say all this and will add that I would really love to believe in something greater, and I'm open to it. I just haven't seen enough to convince me. I used to be a believer and I'm not anymore, Maybe one day I will be again.