Humor can be painful because there's a grain of truth in every joke. For example, think about some of the jokes that are considered crass and offensive in American culture: bits about black people being poor; women being treated as housewives. While the stereotypes are false, they relate to deep-rooted societal problems. Income inequality is still associated with racial inequality. Women are still underpaid and under…
I agree that there is something anarchic, sometimes cruel, inside humor. However, though pain is a useful ingredient, it ought to be one's own--the difference is comparable to the difference in cooking between butter and margarine. Richard Prior telling his own jokes was great; a white guy doing Richard Prior's material is just uncomfortably weird.