As the religious pluralism of America increases, so must the sensitivity of people increase. The fewer traditional Christians there are around, the less people can assume that everyone is celebrating the usual Christian holidays and doing the usual Christian things. Being civil and polite require accepting the presence of such differences and not making them a point of contention or conflict. Unfortunately, Christian Nationalists aren't interested in this and they are deliberately using Christmas as a rallying cry for their dominionist agenda.
Tolerance for minorities and America's diversity of beliefs is being reframed by Christian Nationalists as "intolerance" for the "majority" -- as if the majority needs it's beliefs to be endorsed by the state in order to feel validated. It's a battle over the "ownership" of public spaces. Christian Nationalists think that they should "own" the public square and are unwilling to share it equally with all members of society. Their agenda is labeled "dominionist" because dominion is exactly what they are seeking: dominion over the legal, political, cultural, and economic institutions of all American society.
This is an agenda which needs to be opposed in the interests of liberty. Christian Nationalists have chosen to make Christmas a subject of their war against modernity and modern culture, so it's appropriate that they be countered here as well. If opposing the Christian Nationalists' agenda for dominion means standing up to some of traditions and expectations of Christmas as well, then that's the way things have to be -- and perhaps a bit of cultural dead weight can be tossed over the side in the process.
The above image is taken from a World War I poster depicting a British soldier standing over the body of a dead German, demanding that the reader "Come On" and do their part in the war against the Huns. This image also demands that people do their part in the War on Christmas because the Grinch was, after all, right in this criticisms. Maybe more children should listen to the Grinch and stop reading that book about half way through.