One issue in the Christmas Wars which was a point of significant debate even before there was a "Christmas War" is the status of Christian creches on public land during the Christmas season. Should the government erect such unambiguously religious displays? Should the government merely allow private religious groups to erect and maintain such displays? To what extent should there also be secular displays of secular symbols at the same time?
Because Christian Nationalists perceive Christmas as "their" holiday and the entire season as essentially "their" time to celebrate their religion, the feeling is quite strong that Christian displays should not only stand alone in the public square, but also that they would ideally be erected and maintained by the government. After all, if a community is majority Christian, then a Christian display during a Christian holiday season just reflects the wishes of the majority as well as the culture of the area.
This mistakenly assumes that all Christians accept creches as relevant displays that represent their own beliefs. It also mistakenly assumes that a majority can vote to authorize the government to favor, endorse, or promote the religious beliefs of one segment of the population, even if it's a majority. Doing so is disrespectful of other religions and other religious believers.
Christian Nationalists aren't moved by the principle of treating adherents of other religions with respect -- they sincerely believe that they deserve special privileges from the government. They may, however, be moved by the idea that the government will start treating other religions equally, for example by putting up religious displays that Christians don't like. For Christian Nationalists, their support for having "more religion in government" ends quickly when they realize that "religion" may include more than their own.
The above image is taken from a World War II poster exhorting soldiers to take good care of their boots -- it has no direct bearing on the war itself or the causes at issue in the war. In this context, however, it seemed an appropriate image to depict how Christian Nationalists seem to perceive the alleged threats to their treasured religious symbols.