This poster was found at atheism.about.com. It leaves no doubt as to the motivation of many atheists, and how they want to remove religion from Christmas.
Here is an excerpt from atheism.about.com that accompanied the poster:
Christian Nationalists aren’t moved by the principle of treating adherents of other religions with respect—they sincerely believe that they deserve special privileges from the government. They may, however, be moved by the idea that the government will start treating other religions equally, for example by putting up religious displays that Christians don’t like. For Christian Nationalists, their support for having “more religion in government” ends quickly when they realize that “religion” may include more than their own.
The above image is taken from a World War II poster exhorting soldiers to take good care of their boots—it has no direct bearing on the war itself or the causes at issue in the war. In this context, however, it seemed an appropriate image to depict how Christian Nationalists seem to perceive the alleged threats to their treasured religious symbols.