I do think people who dismiss religious people as believers in 'flying spaghetti monsters' but celebrate Christmas are hypocrites. And you can squeak about culture/Yule as much you like, they're still hypocrites.
No they're not. It's natural, and traditional, to celebrate changes in the year and that goes back to prehistoric times. Christmas was pinned onto the traditional winter solstice celebration, and Ester onto the spring one - to make them acceptable to those who the church wanted to convert. As a human I have a natural inclination to have a brightly lit party in the middle of winter, so I will thanks, even as an atheist.
Most of what happens at Christmas is related to the old traditions - feasting, lights, singing and dancing, the tree, decorations. The Christ association is purely a cynical hijack and in fact I find Christ's birth story one of the least Christmassy things about Christmas. Not least because it didn't happen then, it happened somewhere warm and so the imagery is not winter-festival-ish, and because it doesn't really go with the rest of it, unsurprisingly.
As for Father Christmas, that's just another complicated and culturally morphed tradition. The whole thing about people thinking children have to believe it and "the magic of Christmas" annoys me, because you can still have plenty of fun without actually believing it, but I played along until the kids saw through it because it's what all their peers are doing and it would be mean not to.