These OCD-riddled neighbors were being toxically invasive. It sounds like they were trying to micromanage what this guy did with his property, and specifically had a serious bone to pick with him about his dog's unavoidable bathroom breaks. Long story short, they get so triggered that they threaten to hurt the dude's dog, so he retaliates by planting an army of weeds in their garden under the cover of nightfall. This is just the kind of strategic revenge that we love to see. Doesn't sound like anyone was hurt. Just a whole lot of frustration.
If you're looking for more juicy revenge drama we recommend that you check out these two fitness bullies from a spin class losing their jobs in a tactical revenge.