I've noticed over the years that atheists tend to like to say little things to get Christians worked up. They don't tend to bother with other religions though. They like to focus on things like "Well Jesus couldn't have been born in December." or "The holiday called Christmas was based on a pagan holiday that they stole."
I just want to say "Yeah, and what's your point? Nobody's making that argument."
Yet somehow, I see those same people buying their kids presents on Christmas. I don't see any of them telling their boss that they want to work the last week of December when everyone else is off.
There's sort of a progression from agnostic to atheist. Agnostics tend to be reasonable people and respectful of others beliefs, but a lot of times atheists just come off as jerks.
I have my own reasons for not being an atheist. I've had some life experiences that are good enough evidence for me. And the fact that none of that would ever convince an atheist doesn't bother me.
Its probably a case of what you know. In the West, generally the most prominent religion we are exposed to are various forms of Christianity, so atheists in those parts of the world know what is "low hanging fruit" with that religion.
The thing with the Christmas holidays, particularly in the West, is that they are largely secular in nature now. What does buying presents, eating a meal with family, or putting up a tree have to do with any religious text? Many of the traditional elements of what we consider to be integral to a Christmas celebration are re-appropriated from various other cultures and religions to the point where its extremely easy to have a Christmas without Christ. I've been doing it for years. There is a tree in the living room, I had dinner with my family, and there was some gift exchange but we never went to church or said any prayers. I suspect I'm not the only one who does this. I love Christmas, people are generally in a good mood, there are lights, there is food, and as a fat guy I love the fact that people make cookies.
As for people being jerks, well, yeah. That can happen, and its a bit unfortunate. I understand it at some level, but at the same time I think there are better ways to communicate with people than being a snarky prick. Sometimes it is a bit necessary to not be overly polite in order to be heard, but at the same time its not any of our business what people wish to believe. The only time we have any cause to complain is when those beliefs affect us. If I had kids, I'd be awful upset if they were being taught scripture in school for example. I suspect most Christians would have the same objection if their children were being taught some other scripture.
Anyway, Merry Christmas and other winter holidays to you