Most atheists simply do not have a god belief.
Some atheists are fundamentalists about it.
We do not oppose all religions, just religious expression that intrudes upon the lives of the rest of us. We respect any private expression of religion, and denounce only that religion which forces itself upon others. Also, when people try to convince us to join their religion, we will explain to them why we don't believe. But this is only when they bring it up. I never walk up to a religious person and try to set them straight.