That's controversial at best. Arguably, part of the reason the police is so aggressive and distrustful when interacting with regular people is the higher gun density in the country.
I mean, maybe if you chart violence (y axis) vs percentage of gun ownership (x axis), you get a bell curve and the US is in an awkward middle position. But that's a maybe, and, anyway, that means that both increasing and decreasing the number of weapons would reduce violence in that case.
The vast majority of police violence we witness in the US is against totally unarmed people. I think this gives the police far too much credit. Being a police officer is actually a very safe job to begin with, and violent crime in the US has been decreasing steadily for decades.
In fact, most of the worst offending police departments are the places in the US where the incidence of civilian gun ownership, legal or otherwise, is lowest: New York, Boston, Chicago, LA.
The cops simply don't need an excuse for violence, they're violent even, or perhaps because, the public they attack are unarmed.
The Black Panthers had it right.