Hypocrisy of celebrating religious holidays
This argument may be used by a theist to criticize atheists or those of different faiths for celebrating a holiday based on a faith not their own. The argument does not actually address beliefs about the nature of reality, and instead focuses a personal attack on the atheist or person of a different faith. This is the logical fallacy of the ad hominem, whereby one attempts to undermine the truth of a conclusion based not on evidence or reason, but by a personal attack on the holder of the conclusion. As such, It doesn't serve a productive purpose in a sincere discussion and should be called out as irrelevant to any question of the existence of gods.
It may be useful to point out that, for atheists, the holiday in question is not celebrated for its religious values, and that the holiday also is not recognized by the government for its religious values. It is difficult to argue that an atheist is hypocritical for taking a holiday off, when society-at-large recognizes it as a day traditionally taken off from work and school. It is obvious that the widespread celebration of Christmas is as much a cultural/secular celebration as a religious one. To be a hypocrite on this matter, an atheist would have to both reject the Christian narrative of Jesus, while annually pretending during December to believe it for personal gain. However, since Christmas is celebrated without regard for personal beliefs about the existence of Jesus, no such hypocrisy is necessary or prevalent among atheists.
It is important to point out that a number of major religious holidays have been scheduled to co-opt existing holidays of other religions, such that the new religious tradition claims the day for itself. Both Christmas (see The sun in religion) and Easter are old pagan celebrations subsequently claimed by Christianity. Just as a pagan holiday was co-opted by Christians, a Christian holiday has been co-opted by society-at-large. Many pagan elements are still celebrated by religious believers, such as Easter eggs, the Easter bunny and Halloween.
Another thing to point out is that we regularly denote the passage of time based on religious mythology we no longer accept. For example, the name Thursday originally celebrated the Norse God of thunder, Thor. In fact, every day of the week originally was a celebration of a Roman, Norse, or pagan god. The names of months, too, often have similar mythological origins. Are we hypocritical to recognize such days and months when we no longer hold such beliefs?