I was wished a happy holiday by someone. I told this person I'm Christian and that it's OK to wish me a Merry Christmas. This person knows I'm Catholic yet still didn't feel it was safe to wish me Merry Christmas. 

I think it's more offensive to treat someone's holiday as a dirty word to be avoided via a euphemism than to accidentally wish someone the wrong holiday. I know someone Jewish who thinks all this PC stuff is way out of hand and is not the least it offended if someone wishes him Merry Christmas.  He will probably observe the day by going to a movie and Chinese food anyway, and is more concerned over an Islamic terror attack than being wished a Merry Christmas by a well-meaning person. I think this is keeping things in proper perspective. 

In the United States, Christmas is a public holiday and people get the day off. Some people observe the secular aspect without any religious undertones. This is all a very first world problem.