I don't understand how people can make statements with this when it is so at odds with the facts.
The homicide rate in Baltimore in 1911 was 5.8 per 100,000. Last year it was 37. Was Baltimore less unequal during the gilded age, long before the progressive income tax and federal welfare? No way. Obviously poverty is also way lower today.
The differences are even more stark when you compare modern Baltimore with a place like Edwardian England. Again, England in the early 1900's was massively unequal, had massive poverty problems. But it had homicide rates a tiny fraction that of modern Baltimore.
Why do the U.S. inner cities have so many more homicides than any slum in China or India?
Read the book Ghettoside or Don't Shoot. Crime happens when people can get away with it. Crime happens when cultural and legal sanctions against crime don't get enforced.
I do understand. People have one explanation they like that fits with their politics, and anything else is to be made to support this or discredited. Think of this as a religious approach to policy.
The ways poverty and extreme inequality affect culture and law outcomes are fairly profound though. Cops are loathe to arrest wealthier people on drug offenses considering the legal costs that can ensue. Put enough people in poverty together and desperate behaviour of one kind or another can become normal.
(BTW, what's the excuse for the US sending killers across the world to steal control over people's resources? "Amusement and status" as well? Such answers lack any systematic analysis. Not to mention consistency; you could apply it to any ethnic group. Unless of course there's racist motivations...)
Part of the problem is that structural inequality is supported by primitive racist belief systems like Social Darwinism.