Reading this made me feel very sad, and glad my family have been so awesome about my stutter. Basically, what your dad is doing is not cool. That is NOT how people treat you in "the real world". Besides, even if it was, is treating you like shit going to make your situation any better? I feel, personally, that confidence has a big sway on how severe your stutter is. If he's stripping you of any confidence you have he's making things worse for you, and you need to tell him this. I'm not going to suggest you cut him off or anything, but it does sound like he needs educating. Empathy is a basic human trait.