For a lot of people that do not celebrate Christmas, it's very annoying to live in a supposedly secular nation that is so heavily entrenched in christian dogma. Christmas isn't just a brief celebration anymore. It takes up the entire month of December with decoration, music, and television programs. It even worms it's way into November, with store displays and other commercialism aspects. As Rudolph Quin mentioned, it isn't the holiday itself that is offensive. It's the overbearing domination it has over the culture that is offensive. It simply makes people who do not celebrate it feel like a minority. Then add in the fact that any slight against Christmas automatically makes you some kind of villain. It's all over the media, with this supposed "War Against Christmas". Our culture automatically alienates and criminalizes (to an extent), those that speak out against Christmas (and Christianity as a whole).
The majority religion in the US is Christianity, and those who don't celebrate Christmas
are a minority, and the media, companies, stores, etc. are going to cater to what is in high demand, and thus it has lead to Christmas being a very prominent holiday in our country. This isn't the government's doing though. Sure, there are issues in our country that do have an unnecessary religious backing, but Christmas is one that I feel
people shouldn't have to lighten up on. Aside from politics, work, and school, I think everyone should be open to religious expression and I'm sorry that the majority celebrate Christmas.
And the attitude thing can swing both ways. I've met people who were rather smug about not celebrating Christmas and liked to belittle those who do. Coming from my perspective, I personally don't care if people don't celebrate Christmas and don't like it (and I won't push it on them either), but what I don't like is being treated like an idiot because I do.
This comic I made a few years back is a bit relevant to the thread haha.