I dunno, that and Easter are like the only things close to a holiday Christians have, and Im sure the reason they removed it from their cups is because of the word Christ, being a holiday based on His birth and all.
Although I dont really find this to be a huge thing to protest over, I do find it to be kinda crappy of people to do. Same thing with banning the manger scene from public places. Its the first small step to banning Christ, I think.