I think Thomas feels he is losing the parts of his culture that gave him the warm fuzzies at this time of year because of some amorphous but malevolent hegemonic, cultural/political force made up of lefties, the Lifeboat News, liberals, ISIS, family, etc, and wants to let us know that he is not happy about it/us. The "Christianity" he describes as under siege appears to be as much an incoherent conceptual jumble as his notion of the enemy that is supposedly at war with it.