So now you’re trying to say we should just go back to 1930’s New York (and prisons!) and tell them they should just stop forming those ethnic gangs because clearly they don’t actually need to do that, and they’d be better off without them?
Hey, you’re welcome to if you want. Time travel may be hard, but I’m sure someone would let you into your local Folsom equivalent if you asked.
We do tell people not to form ethnic gangs, it is called "the fight against organized crime."