How we cite our quotes: All quotations are from Harry Potter and the Sorcerer's Stone.
Quote #7
RON: Trevor…shh! Go, you shouldn't be here!
NEVILLE: Neither should you. You're sneaking out again, aren't you?
HARRY: Now, Neville, listen. We were—
NEVILLE: No! I won't let you! You'll get Gryffindor in trouble again! I-I'll fight you.
Duty can sometimes lead allies to fight. Neville doesn't see the whole picture here. He only knows that Harry and his friends are getting their House into trouble. So he does something he's scared to do because he believes it's the right thing: an honorable (if misplaced) sense of duty.