I am not bothered by company or group sponsored events being billed as Winter Celebrations or just plain old "Holiday Party". I like the idea of it being inclusive of all celebrations. Even if a person does not celebrate Christmas, Hanukkah, Kwanzaa, or Winter Solstice, they probably at least recognize New Year's Day according to the Western Calendar.
But I draw the line at someone saying that no recognition of the holiday season can occur. And a co-worker can not decide how I can decorate my office space. I think I'd be setting up a rotating holiday theme switching up to all the major events from mid December to post New Years.