I had a great neighbor when I was little and then when I was 10 his dad moved in and evicted him and since then my poor father has had to tolerate their insanity. It runs the gamut for crazy behavior. Everything from revving their engines of snowmobiles and lawnmowers well past midnight to threatening my dad claiming we were stealing their cable and siphoning electricity...ugh.
One day I was visiting my dad and I had my baby girl with me. The lady comes over waving a diaper in my dads face calling him all sorts of names and claiming he threw the diaper in her bushes. The houses are right near a highway where people throw all sorts of stuff onto our lawns. Diaper was the wrong size and brand to be my daughters but the lady didnt care. They get off on confrontation. They have a junkyard behind their house. They piled up every dead vehicle and piece of trash they could back there. We thought it was ridiculous but fine since it was their yard. Then they call the township on my dad for having not cut his grass and for having two vehicles (that were driven regularly) parked on the opposite side of the property from them. There was a pole barn in between them and the vehicles so they were entirely out of sight and as I said they were driven regularly. Some people just suck.
Some people really do live off of confrontation, I can't understand it, but not much of a way to fix it... I hope things get better for your dad!