I always roll my eyes at people who present this argument as a way of justifying celebrating a Christian holy day, while having nothing to do with the observance of it.
There is no point in debating, half educated pedants. It only annoys you and does nothing to elevate the pedant’s IQ. My standard reply to this inanity is, “it was always a religious holiday.”
They either walk away confused, sneer at me for my “ignorance,” or best of all, step into the bear trap and try to debate me on the subject.