The interesting thing about the Pattersons' habit of thinking that they have to avenge themselves on people who they judge as deserving it is not just that we're dealing with a clan of vindictive, nihilistic and cynical imbeciles who can't picture a world in which people who enjoy themselves aren't doing so to enrage, humiliate and ruin their lives. The interesting thing is their reaction to being the victims of the same sort of horrible people that they themselves are.
As we all know, about fifteen or so years ago, a bunch of jerk kids had nasty fun smashing John's model train layout. As we also all know, the Patterswine made a bunch of ill-informed noise about how a lower-class kid corrupted kids from good homes into ruining things for people because that's just what poor people do. Not only is this an atrocity because Lynn equates not having enough money with moral inferiority, it's morally false because Lynn doesn't understand vandalism.
This is because it seems to me that the kids honestly seemed to think that John was trying to be a dick to them by having a good time when they were miserable. It's not that there's a yawning hole in their psyches where the ability to enjoy life is, it's that people are stealing an ability to feel happy that they never had, do not have and never shall have away from them. The closest they can come to real happiness is a vindictive outburst of rage against their alleged oppressors. The reason that I find this interesting is that I've not only described the choads in the balaclavas going smashy-smashy, I've also described the Foobs.
The end result is that one set of narcissistic sociopaths with a vindictive streak have to deal with the ugly antics of people just like them and they don't like it one bit.