The danger for them is that they lose their grip on values and become the very criminals they are fighting. In one case, FBI agents barbarically tortured a man. In other cases, the police have turned to the same crimes as the crooks. The mafia forces compliance from people in illegal activity. After a while those compliant people are accomplices.
People can become good people, separatists, or bad people through exposure to their environment.
Some slide into the new role, and some are forced to change and transform their personality because of it. Frontal lobotomy is a very radical procedure that has been used off and on by psychiatrists to prevent destructive behavior. Severing the connection between the front lobes of the brain makes the personality placid - apparently prevents strong motivation or overreaction from occurring. It is only used as a last resort. Either that or he was just an irascible and incorrigible poet who was prone to violence.