Is it rational for, say, Muslims to not celebrate Christmas?

[rado84]

The few Muslims I've asked about this all say they do not celebrate Christmas, yet I'm an atheist and still celebrate it as a secular holiday, as I'm sure do most here - winter solstice and all that. Communication breakdown or...what?

Muslims don't celebrate it bc they think it's a christian celebration when it's not. How could they know it's actually a pagan celebration, dated long before the single god was invented?
I don't celebrate it either. To me it's just another day of the year. I don't put up a tree inside and since we have 11 cats, now I have 11 more reasons not to deal with the stupid tree (even though it's plastic). I don't buy presents for anyone and I've told my friends I don't want any presents (unless these presents are in the shape of a CPU or a video card - then it's OK ). Fortunately all of my friends are atheists and have the same vision of christmas like mine.
In my language the christian greeting for christmas can be either "merry christmas" or "merry christ's birth". If someone outside of my circle of friends greets me with the latter, I respond with "merry Horus' birth" which infuriates them a lot.    

P.S. I'm writing "christ" and "christmas" without capital letters not because I'm illiterate. I'm told that capitalizing these words expresses respect for jebus christ and since I have absolutely no respect for a 2000 years old zombie, I write its name without the capital letter.