Ethicists study ethics. Per your example, I would expect an ethicist to be able to study ethics very well. You don't expect a teacher to know everything, or a w

Ethicists study ethics. Per your example, I would expect an ethicist to be able to study ethics very well. You don't expect a teacher to know everything, or a writer to always speak with perfect eloquence, or a photographer to always take great photos. I don't understand why someone who studies ethics should behave better, any more than someone who studies the human musculature to be able to lift more weight.