Traditions.

One super way to get children to hate their ancestors is to try to get them to appreciate the latter's deprivations. Take a kid who wants an Xbox for Christmas more than he's ever wanted anything since his first breath. Tell him that his forebears in England considered themselves blessed on Christmas morning if they got an orange and an apple in their sock. If they got a pear they would do the Happy Urchin Dance on the cobblestones in their bare feet. Today's kid can put his hand on an orange or apple or even a pear anytime he wants, but is always trying to get potato chips or chocolate. Does he say, "Well, Grandfather, I understand that I have been acting spoiled, and will be happy with anything I may get on Christmas morn"? Oh, probably not.

Then there's the bizarre traditions.

"Back in Gzrdsk we used to gather around and play games on Christmas afternoon. Like Drop the Pickle. That was an old traditional Gzrdski Christmas game, Drop the Pickle. It took a lot of skill. You couldn't just drop it. You had to drop it right. That is, if you wanted onions and cream after."

"I hate tradition!"

"Onions and cream like we used to have in old Gzrdsk..."

"Ugh!"

"...brined peppermint...cabbage stuffed with hay...elk knuckles..."

"I'm glad you moved to the United States! We have CANDY now, Grandpa! CANDY!"

"And then we'd all gather around, and Uncle Plsk would tell us how Gnarled Witch Yaga would sneak in on Christmas Night to bring presents to the good children and take a bite out of the bad ones."

"AAAAH!"

Drop the Pickle is harder than you'd think.

Life was tougher in the old country, whichever old country it was, and we probably could benefit by toning down some of the insanity and materialism and commercialism in the modern American Christmas. On the other hand, nobody likes a party pooper. 

Or onions and cream, for that matter.