This whole post is sort of tongue in cheek but let's see if it sets up a useful discussion: It seems to be a classic joke that holiday meals which bring together scattered family members or acquaintances of different viewpoints are ripe for all sorts of disputes when people have a few too many drinks or otherwise drop their normal veils of diplomacy. I gather that can especially tend to happen when out-of-town house guests overstay their welcome!
The running gag most of the time is that people have their worst falling outs over politics and religion. The former is not within our forum scope of discussion, but the latter is, especially if we brush past the narrow sectarian disputes and go to the heart of the issue.
So here's my proposed list of "Issues Worth Fighting Over During Holiday Meals" for an Epicurean confronting disputatious non-Epicurean acquaintances. Most of time here on the forum or in the real day-to-day world we approach these issues diplomatically rather than saying "you're full of bunk if you believe that!" -- but if a family member drinks too much over the holidays and gets in your face, these issues stand out in my mind as non-negotiable and "worth fighting over." If you have to alienate your brother-in-law forever, at least make it an issue worth fighting over, like one of these:
- There are no supernatural gods. ("Your god doesn't reign, buddy!")
- There is no life after death. ("You only go round once, buddy!")
- Some things in life are knowable with certainty. ("Your radical skepticism is bunk, buddy!")
- Some things in life are under our control. ("Your hard determinism is bunk, buddy!")
- The feeling of pleasure and pain, properly understood, is the guide of life. ("Your absolute morality is a fantasy, buddy!")
- Virtue is not its own reward but is a tool for achieving a pleasurable life. ("Your "virtue" is the handmaiden of pleasure no matter what you say, buddy!")
I suppose we could also consider things like "The sun is the size it appears to be!" or "All sensations are true!" but those might require a little more concentration than an obnoxious or inebriated relative could muster. And only a few would get stirred up if you call Aristotle a "Debauchee" or Democritus a "Judge of Nonsense!"
I think this list is a good start, but I may be missing some, so please remind me if there are others.