People are stupid

People will fight over the stupidest things in the world. I share a house with my brother in a nice neighborhood on the bay. The past six weeks or so, my brother and the neighbors one block over have been feuding.
It all started when those neighbors decided that they didn't want people walking in front of their house. Their house faces the bay, with nothing between them and the water but a sidewalk and a seawall that the county owns and maintains. Because the sidewalk and seawall are owned by the county, many people in the neighborhood walk along the water on the sidewalk. The sidewalk is relatively new. The county put it in about a year ago when they rebuilt the seawall after a hurricane damaged it. Before the sidewalk was put in, no one realized that my neighbors property didn't actually go all the way to the water. So people didn't walk in front of their house, since they thought it was private property.
After the sidewalk it became quite common for people to walk in front of their house. This bothered our neighbors so much,that they put up signs at each end of the sidewalk saying that the sidewalk and the seawall were private property. When they first put the signs up, they told us and others in the neighborhood, that they were putting them up to keep people from outside of the neighborhood from fishing in front of their house. That seemed to me to be a reasonable concern, and I could understand their position. The signs worked quite well for keeping people from fishing and walking in front of their house. People who lived in the neighborhood knew the signs were bogus, and ignored them, at least for walking. Everyone seemed happy.
Then those same neighbors took a dislike towards my brother. I don't really know why they decided they didn't like him, and I really don't care. The problem was that they started telling him he wasn't allowed to walk on the sidewalk or on the seawall because they owned it. This is the exact wrong approach to take with my brother. Since he knew that they didn't own it, them telling him they did, made him mad. He started deliberately walking on it every day.
The first few days, they just had shouting matches. With them yelling at him for walking there, and him yelling back that he had every right to walk there. Since that wasn't getting them anywhere, they called the police and reported that he was trespassing. The police came out, but my brother had already left for work by the time they came. So they left him a warning. The same neighbors also came by the next day, to make sure that we had gotten the warning, and to let us know that the police had told them that "they take trespassing very seriously."
Before this,my brother had been positive that he was in the right. Now he wasn't so sure. So for a few days he didn't walk there. But it bothered him so much that the neighbors had "won" the dispute, that he called up the county appraisers office. The county appraiser confirmed that the sidewalk really was public property. So my brother went back to walking on it and arguing with the neighbors. After all, he wasn't going to let them win.
The neighbors again called the police,and again my brother wasn't home and another warning was issued. My brother ignored the warning, but did go down to the appraisers office and had the appraiser print out a plat showing the seawall and sidewalk as public property. The county appraiser called the sheriff's department and let them know that the seawall and sidewalk were public property. My brother kept a copy of the plat for himself to show the cops if they ever came back out, and the other copy he proudly presented to the neighbors.
They were so upset, that they called the appraiser and tried their best to convince him that his plats were wrong. They also called the cops yet again, but this time the cops didn't issue a warning or even attempt to talk to my brother.
So, that is where we stand today. My brother walks in front of their house on purpose to annoy them, and they regularly call and report him for speeding and trespassing. They also have a yelling match about once a week with him.

This whole issue is so stupid on both sides. On my neighbors side, what does it hurt them if someone walks along the seawall in front of their house? It's not like my brother was parking himself in front of their house fishing. All he was doing was walking past.
And on my brothers side, what does it hurt him not to walk there? He could go around, or simply not walk that direction. Go the other direction on the sidewalk.

Why do they both have to fight over such stupid things?

By the way, the picture above is of the seawall and sidewalk that caused so much trouble.