yes extremists are everywhere but a single extremist can be controlled while group of extremists end up doing 911 stuff. Atheists don't force people to dump their religion and try to convert them to atheists. While every religious person thinks he's on the right path and if that person is extremist he'll do anything for his faith.
Eskimo: "If I did not know about God and sin, would I go to hell?" Priest: "No, not if you did not know." Eskimo: "Then why did you tell me?"