My contention would be those people arn't celebrating christmas. You can give gifts hang stockings and put up a tree, doesn't mean your celebrating christmas whether you call it that or not. Since all those traditions were taken from pagan rituals, you are celebrating those. If I decide to fast during the same month as Ramadan but it has no spiritual meaning to me, am I celebrating Ramadan? No that's absurd. Just because you take actions mimicking a religion without following the meaning behind it does not negate the fact it is still a religious holiday.