It never makes any sense to me. You'd think they'd stay focused doing things they enjoy and let others alone.
Understanding why people spend time bullying someone else is difficult for me. I may not agree with or like everyone else but I have no desire to make others miserable.
If I had to guess I'd say there's a lot of sociopaths among us that are incapable of feeling empathy for others and fail to respect the rights of someone else. In this case these people aren't trying to stir up trouble with every neighbor. They seem to maintain on good terms with those that are relatively wealthy and those that have a higher status in the community. It keeps them from jeopardizing their own image amongst those they consider to be their peers.