Why so much animosity between Atheists and Religious Ones?

I simply wanted to post this after seeing so much on YA and in reality. Being a completely faithful Christian man myself, I've had many "conversations" regarding my beliefs and other beliefs with Atheists who are friends of mine in which neither of us have attempted to demean another's belief or force our beliefs on another and spoken very civilly and intellignlently. But I see so much of the exact opposite far too much, from deranged, utterly unacceptable religious freaks as well as pompous, grossly disrespectful atheists equally. My question is, what really provokes you all to be so passionately unruly and wrongful in your approaches to people like that, if you care to answer?