I used to work retail and I never shied away from saying Merry Christmas as that's what 99.99% of people around here celebrate anyways. Also, I never got reported for it, so who cares? I'm not interested in bending over backwards for the .01% as most of them probably aren't offended by hearing Merry Christmas anyways. Heck, it's somehow not ok to say Merry Christmas but it's ok for Christmas ads, banners and all things Christmas to be put up in the majority of public spaces. Hypocritical much?
It's one thing if I were to know someone who celebrates an alternate holiday as I'd have no problem saying Happy Hanukkah to them or whatever and that would be the polite thing to do. However, if I don't know someone I'll just say Merry Christmas. If anything as a Christian I should be offended by this push to further remove the Christ from Christmas. It's become too focused on the superfluous as it is IMHO. Besides, Christmas is just as much a secular holiday now anyways. Is it somehow offensive now that even atheists want to exchange gifts with one another and put a tree up in their house? Who's supposed to be offended by this? I believe in free speech first and foremost. If someone has a problem with something that's not intended to offend them, I don't think I'd want to know them anyways.