What would you rather have.. a mentally feeble, psychologically unstable person performing surgery on you, or a mentally feeble, psychologically unstable giving you a traffic ticket?
You have to graduate from medical school to become a surgeon. The point is moot, there aren't very many licensed surgeons that are idiots. Takes some smarts to get in a position where you have someone's life in your hands.
Cops also has people's lives in their hands as well. Makes sense to have not have a bunch of armed, mouth breathers running around enforcing the law.
The only person saying that we should divert surgeons, engineers, etc in to law enforcement is you.