Maybe they're just setting aside their differences over the holidays. Not necessarily pretending nothing is wrong, but trying to look past it for the sake of having a good time and not ruining it. :/ Of course the issues are still there, but depending on your beliefs and despite how corny it is don't kill me, Christmas is supposed to be a time of forgiveness, love, reflection, etc.
I dunno. 8| Treating it like every other day of the year, picking fights, etc. doesn't really sound productive to me. Maybe just enjoy the lack of confrontation while you can?