How difficult is it to tell your professor to not interrupt you? To tell them that they're completely mistaken, and that their emotional opinion is not representative of the facts of the matter. Murder is a legal term. It refers to unlawful killing. Well there may have been a murderer in a police department here and there, that's not what the professor is referring to. They're mistakenly opining that any lethal police encounter makes a police officer a murderer and it's very very simple to clarify the distinction between killing lawful killing unlawful killing murder etc