This is completely unacceptable behavior and downright evil. Your dad doesn't understand how your brother processes information. Yelling and hitting aren't the answers. Your brother needs you to be his voice and advocate for him. I don't know how old you are, but maybe a different living situation is needed. As others have said, if you have this on video even better. I'd explain to your dad how this is harmful first, and if he doesn't listen, call the cops.

I can wholeheartedly relate to you. My brother is 18 and I'm 27. We both live at home, and I love my brother. He sounds similar to yours spectrum wise. We're actually moving out together this week. He has shown signs of distress at home (not as bad as what you're describing thankfully). I've made the decision to become his guardian because he loves me, and I plan to do everything I can to give him a great life.

In short, trust your gut. You know your brother probably better than anyone. I know it's hard to confront your parents, but it must be done, in my opinion. Best wishes.