First of all I think we're all clear he's a jerk.
Secondly, as someone who does get poop/rat in lawn every time and again, I understand his frustration. However, if he has really been at war with the neighbors, this is just the weapon he needs. Take that cat to SPCA, complain to town council, and make the neighbor eat humble pie and train dat cat otherwise be made to pick up the poop every day.