Also in the sense of literally trying to outlaw Christmas. The Bible doesn't describe a Christmas festival and celebration, so many Christians felt that it was improper and unchristian for a very long time.

In the US the only real war on Christmas was fought by Christians. The soviets, the CCP and briefly the French revolutionaries are the only times atheists have actually pushed against it. The Nazis were in favor of a pro-nazi version of Christmas that was more about the state.