goodness, we gonna go all south park & ruin christmas here?
billions of people celebrate it. 90% of those have no religious motivation, its just a fun season with foolishness, food, and loot for most.
If you don't like the tree, don't place one, or -- I stuffed mine under the floor for the bonus but will never see it again.

lots of games have seasonal silliness. People enjoy this stuff, and its harmless. I set off virtual fireworks/lightshows for dwali (sp?) too, and I am not hindu.