No one is against Christmas trees. What people are against is having the government promote a religion. "Holiday" tree allows the tree to go up w/o violating the Constitution.
You can put a "Christmas tree" up all on you, on private property.
The dumbest part about you getting offended is that the origins of the tree are PAGAN, and NOT Christian at all. The Bible even says NOT to decorate the tree as the pagans do. (Jeremiah 10:1-25)
Try reading your bible....
(PS - there are Christian sects that do NOT put up a tree for EXACTLY this reason.)