For us this wasn't a battle I wanted to fight. I don't like pizza crust either... the crust of bread is tasteless... and the crust of toast hurts my gums to chew. LOL, therefore I feel the non-crust-eating thing, is legit!
I make him two pieces of toast, cut the crusts off and call it a day. I feel he (my kid) doesn't need more than two pieces a bread during a meal, so if he wants more - and the issue is he is still hungry, I offer him to healthy choices.
Good luck!