How come nobody is talking about this?

at Xmas time my coworkers usually go over and beyond to fill in holiday hours so the rest of us can enjoy our holidays and that the same courtesy should be extended to them.

Just to be clear, it sounds like this is the case. Foreign coworkers have religious times they honor that are small, bur regular. Local coworkers have religious times they honor (Christmas, Easter, etc) that are large, but irregular. OP is an atheist, so has decided they are entitled to both the foreign coworkers religious times AND the local coworkers religious times?

If my assumption above is correct, you're totally the asshole. YTA.