Not that I've studied this area deeply, and I am well aware of the pagan origins mentioned, but from what I heard at the Bible study last night, Christmas traditions as we know them today have come from Christians trying to turn those pagan traditions around in order to point the people they were ministering to to Christ.
Like the Christmas tree came from someone (forgot his name) going to a town and after cutting down an oak tree they worshiped he told them instead to put fir trees in their homes to remind them of Jesus--because fir trees are evergreens--green even during winter--and can represent eternal life in that way. And lights on the tree because Jesus shines even in the darkness.
Just pointing that there's more some might like to consider. History can be a tricky subject since deciphering the past accurately can be pretty tricky and historians often disagree with each other.
In any case, it personally doesn't matter much to me what Christmas used to be, but how and why it's celebrated today. People have different POVs on that, though, and I think people should do whatever they think best. It matters little if someone decides that they'd rather not celebrate Christmas on moral grounds, and it's certainly not my decision to make for them.