Mostly it is. city-data.com has demographic and crime stats for every city in the US. Find me a majority black city with a low crime rate. Find me a city that's less than 5% black with a high crime rate. As an exercise, scroll down to the murder stats, then try to guess the demographics.
Violent crime is a black phenomenon in the US.
I don't dispute that, but the "mouth jewelry" idiocy is being copied outside that group. Some of the first websites that sold that garbage (noted and laughed at in this forum) featured pictures of white teens and young adults.