True believers, whether christian, muslim or whatever, want to convert you, they want you to believe what they do, and they're willing to go to extremes to make it happen. Atheists don't really care what you believe, and don't go out of their way to convert someone.
http://ow.ly/vN1JZ an example of what believers in power do to suppress any difference in thought
http://ow.ly/vRaEo an example of why believers want to suppress different ideas (because they can't win in a fair fight, that's why)