There are actually documented cases of police officers in the early 20th century requesting heavier calibers and hotter loads from gun manufacturers because they believed their firearms were incapable of stopping an enraged <slur deleted>.

Biologically, this is utter nonsense. But the belief that black people are tougher, stronger, and more capable of withstanding pain and drugs is a surprisingly common belief. Doctors are notorious for downgrading black pain in clinical situations as compared to white patients, and administer less pain killers.