Fix your own issues before fixing your neighbors is my policy.
No idea what you do for a living ( you indicate a "uniform" ), but the actual reason why many States have the front and rear plate law is not because of cameras, but so that the LEO or State Trooper can read your plate coming and going. Sure your neighbor got you for a missing plate - whoopee. Guess what? He's right. Mount the plate.
As for your neighbor and you...
Either get your XJ off the street and mind your own business, or politely go speak with your neighbor, or both. A lot of times, new people to the neighborhood get this "we have to improve things" attitude and tend to rock the boat a bit. I also think he's bored, or something is happening in his life which isn't even your issue. Believe it or not, it's normal.
If you both continue down this nuisance phone call stuff, the Police will stop responding to either of your calls, which will make it a bitch if there is a real problem.