So Matt has had a rough past, but we've all established that. We've also established that he doesn't see anything wrong with the way Stick treated him. And that remains the case until the same happens to Foggy.

Maybe he's assaulted as an adult, or in college, and at first, Matt's like "Ok, so this isn't a big deal, right?" but then he hears Foggy whimpering, groaning in pain, and Matt realises he needs to help out when his protective instincts for those in need, and for sweet, harmless Foggy who's never hurt anyone. And as he's helping, he realises that the way Stick treated him wasn't right.