According to The Onion, you should not attend your office holiday party. But if you choose to ignore that advice, you should under no circumstances give a six-hour lecture on how “Christmas” evolved from pagan winter solstice celebrations. Because “No way you can cover all the relevant material in less than eight. And remember to build in time for questions!”
I say make it a double header and add at least two hours on the pagan origins of Halloween (spoiler: it involves fairies). I can see how this can be annoying, but it is still more interesting than whatever it is that “normal” people jabber on about. Perhaps what we introverts fail to understand is that the jabbering itself is the point, and the content mostly irrelevant.
Happy holidays!