If they were truly secure in their non-belief, they would not have to resort to this ridiculous behavior.
I heard a Pentacostal minister give a good explanation of some athiests. On the outside, they try to put forth an argument that there is no God. On the inside they are shaking their fists toward heawen while screaming “No, God!”.
That's actually true. When I first realized my faith in God was a sham, I was very defensive about religion. Now it's 15 years later, and Islam is the only one I still pick on (because I think they're awful.) But I treat Christians and Jews with respect and don't pick fights with them.