Sure...replace "atheists" with "Jews", or any other religious or ethnic group, and ask then if you'd defend it as you are.
While you're at it, imagine you're a reporter, say, from a news network doing research for a story about conservatives and Christmas. You find this thread.
Care to guess, what with some of the quotes, what'd be written? The President himself would disavow this site.
Okay so you think its not offensive when Atheists say bad things about Religious people? Because I have heard equally offensive statements by both sides.
Also don't pull that "replace x with Jews" people do that WAY to much for it to have any impact.