Pagans enjoyed winter solstice. The Christians thought that the Pagans should worship Christ, instead. So Christians borrowed from Pagan festivals, rewrote some history books, and then converted many Pagans to Christianity. Probably under threat of persecution, purgatory, or threat of being burnt alive.

Fundamentally, winter celebrations are frivolous fun. People are free to believe whatever they like (so long as it does no harm). The trouble starts when governments give preferential treatment to one religion over another. This means that neither Christmas decor nor any other religious artifacts may be put on government property.

This is a difficult idea for fundamentalist Christians to accept because it involves two concepts. The first is called “fairness” and the second is called “preferential treatment”. That is, to be equitable, no religion may be given special attention.