You know the drill: around this time of year the Christophobes try to debunk Christmas by alleging that it’s simply a hodgepodge of pagan traditions that Christians co-opted to ease the transition of converts into their religion.
Mithraism, Vikings, blah blah blah . . .
Yesterday I discovered (thanks to Travis Prinzi of the Hogwarts Professor website) a nice response to this critique of Christmas on the Alastair’s Adversaria blog. You might want to bookmark the entry (or this post pointing to it) for reference each December, as these attacks are unlikely to abate anytime soon.
Merry Christmas, and I hope you’ll all be in church tomorrow!
The Western Tradition 
it’s not just the atheists that make this argument. I’ve encountered Christians who get very upset when you try to put the Christ in Christmas because of the pagan and Catholic associations of the holiday. Thanks for pointing me to this information.
Another excellent resource that examines early Christian references to the Nativity and reasons why December 25th became important to the Church (pre-sol invictus):
http://www.piousfabrications.com/2010/12/pagan-origins-of-christmas.html