My neighbor certainly became offended when I built our privacy fence.
Mind, I do not like the neighbor. In fact, I mortgaged everything I had and purchased the property behind the neighbors house, as well as on the other side of his house. I then had installed a privacy fence on all three sides of him (he can only look out of the front of his house, facing the street).
It is not really a fence. It is more like a wall: 25 feet high and 15 feet wide, with turrets every 20 feet (I was inspired by my visit to the Great Wall of China). It is built of reinforced concrete. I made it 15 feet wide to give the guard dogs plenty of room as they roam the top of the wall from one end back to the other. The turrets are, of course, to house the security guards I hired.
I am now negotiating with the neighbor that lives directly across the street from my obnoxious neighbor. Should I successfully purchase that property I will then seek permission from the city council to extend the wall (on either side of the obnoxious neighbor) from my side of the street to the other, leaving, of course, tunnels for cars to drive through. Should I be successful then the wall across the street from my neighbor will be around 40 feet high.
I have decided against having cannons brought in and aimed at his house, as going too far. I do not want to be thought of as extreme.