I am Not a Pagan Either

I would guess that most atheists in the U.S. celebrate Christmas, but that would just be a guess. I am not aware of a good representative survey of atheists to back it up. While I do not celebrate Christmas, my reasons for not doing so have little to do with atheism. Moreover, I see no reason to criticize those who do celebrate Christmas, regardless of whether they are atheists. Their celebrations do not impact me one way or another because I do not participate in them. All the same, there is one increasingly popular defense some atheists are giving for their celebration of Christmas that I do not particularly understand.

I am referring to what I'll call the "winter solstice defense" since I am not sure what else to call it. It goes something like this:

Christians stole Christmas from the pagans. It was originally a pagan holiday that had nothing to do with Jesus, and early Christians co-opted it as a way of stamping out paganism.

I do not doubt the veracity of this claim. Christians did co-opt this pagan holiday, but I am not sure how this is supposed to explain anything about why an atheist would celebrate Christmas. What does this even have to do with atheism? At best, it might explain why a pagan would celebrate Christmas. Most of us aren't pagans though, are we?

If an atheist wants to celebrate Christmas, he or she should be able to do so guilt-free simply because he or she finds it enjoyable. Why are any other reasons needed?