I'm Catholic but I don't see why everyone can't celebrate Christmas.
The imagery of tree, presents, turkey, mistletoe, etc, don't have a lot to do with the Christian faith and the whole tradition has developed to include elements of all kids of religious practices over the centuries.
I go to Church at Christmas and put up my nativity but everyone should be able to celebrate winter and family at this time. It's the one holiday where family gets together and people seem to genuinely be that bit happier!
I do not, however, have any time for people saying that religious imagery should be banned. If you don't like it, don't look at it.