I think this is "The Place Where Chicago Was", by Jim Harmon, originally published in Galaxy Magazine, Feb. 1962, and available to read on line at Project Gutenberg.
An American 40s to 60s novella read in the 80s. Set near Detroit or Chicago at about the same time.
It was late December of 1983. Abe Danniels knew that the streets and sidewalks of Jersey City moved under their own power and that half the families in America owned their own helicopters. He was pleased with these signs of progress. But he was sweating. He thought he was getting athlete's foot instead of athletic legs from walking from the New Jersey coast to just outside of Marshall, Illinois.
After a nuclear war, broadcast towers have been installed to stop aggression, and nearly all the population have become pacifists and vegetarians. Those people that haven't are shunned as they are seen as dangerous.
...No human being could directly or indirectly commit murder, as long as the broadcasting stations every nation on earth maintained in self-defense continued to function.
These mechanical brain waves coated every mind with enforced pacifism. ...
Pacifism was vital to the survival of the planet.
...
Some minds were more finely attuned to the encephalographic inversion than others. People so in tune with the wavelength of pacifism could not only not kill another human being, they could not even kill an animal. Vegetarianism was thrust upon a world not equipped for it. ...
There is a scene in a diner with a menu board where the prices for steaks etc. are much lower than the vegetarian options.
Ketchup/tomato sauce is also referred to as blood. I remember thinking it was interesting to see the 50c vegetarian referred to as expensive.
The two of them pulled up wire chairs to a linoleum-top table in a mirrored corner. A faint purple hectographed menu was stuck between appropriately colored plastic squeeze bottles labeled MUSTARD and BLOOD.
Danniels knew what the menu would say but he unfolded it and checked.
Steaks
Plankton .90
Juicy, rich-red tantalizing hamburger .17
Accessories
Mashed potatoes .40
Delectable oysters, all you can eat .09
Peas .35
Rich, fragrant cheese, large slice .02
Drinks
Coke .50
Milk, the forbidden wine of nature .01
Coffee (without) .50
Coffee (with) .02
The enforced pacifism is unfortunately having negative effect (not up the "Firefly"/"Serenity" level, but sort of "abandon ye all hope') and a plan is conceived to destroy a tower, which I think is on an island, so that normal humanity can return.
The scheme in the story doesn't quite match this. I also don't see any evidence that the broadcasting towers are on an island. The protagonist does take a trip beneath Lake Michigan by submarine at one point though.
Danniels rubbed his face with his palms. "I'm not even sure if I understand what you mean to do. You want to rocket the H-bombs out almost but not quite beyond Earth's gravitation and explode them so the fallout will be evenly distributed over the surface of the planet. You think it will cause no more than injury and destruction—"
"That's all," Joel said sharply.
Richard gave an eager nod.
They had had to convince themselves of that, he knew. "But why do you want to do anything as desperate as that?"
"Simple revenge." Richard's tone was even and cold. "And to show them what we can do if they don't cut off the Broadcasters." The small man's liquid brown eyes softened. "You've got to understand that we really don't want to kill people. Our actions are merely necessary demonstrations against insane visionary politics. I only want the Broadcasters shut off so I can do efficient police work—Joel, so that he can fight in the ring with the true will to win of a sportsman. The rest of us have equally good reasons."
Fortunately, this plan is never carried out, since the protagonist finds another way to fight the system.
