I was ignorant too once. I heard a guy say FGM was comparable to circumcision and I was so pissed off at him. I went home to read and prepare myself with a bunch of facts to confront him with...in the process i realized he was totally right.
so i'll never forget how hard it is to tear yourself away from something you've heard over and over and over again as truth. At first it so difficult to take new information seriously. So don't take it personally. Its a classroom full of young people.