Most of the actual conflicts that get reported as people being "offended" by "Christmas cheer" or similar involve legal challenges against government entities endorsing or privileging a religious interpretation of Christmas, such as local governments dedicating public space exclusively to a nativity scene. This sort of thing is a pretty blatant Establishment Clause violation. This then gets spun by right-wing media as a "War on Christmas" waged by liberals who hate Christianity, which then turns into parts of their audience believing that saying "Merry Christmas" as a private citizen is somehow a noble act of defiance.