The black comedians that played the chitlin circuit, and the ones that play ghetto clubs now are probably the most brutal in the US. It's expected and respected in the culture, so they learn the ropes fast. If you watch the old HBO Def Jam comedy hours from the early to mid 90's, you see a light version.
That being sad, most of the guys that had long runs playing bars and small clubs before they got famous are pretty good roasters even thought you may not know it unless they are mad at the audience.