"남자는 음식이 아닙니다."
Translation:A man is not food.
yes that is correct but it implies that is as opposed to other men who are food.
I know that "남자" means "man" and "남자들" means "men," the "들" at the end makes it that.
Always remember, if the noun has "들" at the end, that means that it is multiple of the subject.
Since Korean doesn't use articles, you have a bit of leeway. By default, you can use either, but contextually one or the other might make more sense. If one or the other translation is not accepted, but is definitely proper, you can report it and the mods may eventually accept your suggestion.
Duolingo makes me second guess myself when it comes to these bizarre sentences
It depends, I would definitely eat my man (I'm sorry, I couldn't keep it )
I disagree. Odd sentences are usually best, since unusual things are usually more memorable.
I also disagree. At this stage, we have very limited vocabulary, but we have the tools to begin to pick up some crucial grammar e.g. "X는 Y이 아닙니다." We're basically children, and I can imagine saying this to a child in a preschool context (maybe the child is trying to sort pictures into simple categories, e.g.).