Who cares if he was an atheist? The point is to be able to say it/promote it without everyone getting offended, etc.
It's "hysterical", btw.
Much of this has occurred in the work and school place, where children and workers are not allowed to say Merry Christmas or have decorations that depict "Christmas."
But, how do you make a private company change their policies? I mean, a private company may have policies that do not allow christmas decorations or cards that say Merry Christmas, etc. How can Trump intervene? I am assuming that most employees sign some form of contract with their employer and have to abide by such policies. So, where exactly are "we saying Merry Christmas again?"
