"You know nothing about story writing."

I was sitting at a table in art class next to this annoying, rude boy. He was telling me about this fan fic idea he had. 

After I gave him my opinion on it (which he ASKED for), he started acting all offended and said, "No one asked for your shitty input," and "You know nothing about story writing."

This stuck with me because I want to be an author. If I supposedly don't know anything about writing, then maybe I should give up.