Christians & Christmas: A Defense

There's a really tiresome tendency among many to suggest that the Christian holiday of "Christmas" was derived from pagan holidays: Saturnalia, the cult of Sol Invictus, Mithraism...

I'm not sure at all why anybody thinks that's important.  I'm sort of perplexed by Christians (or their hostile interlocutors) who challenge Christianity's right to celebrate nature's turning of darkness to light. I'm not sure how that's either "pagan" or "unscriptural."  That Christianity saw what the rest of humanity affirmed (and it did so early on, at the very latest by 354 C.E.) and affirmed it also strikes me as a good thing. To say that other ancient peoples had looked at the sun's circuits and deduced that the Winter Solstice was a good thing strikes me as highly irrelevant to any Christian practice: it's like saying that Christians got the practice of waking up at sunrise from the pagans.