Whilst I've said about him perhaps not being in control and not being able to help himself, Hellion brings up a very good point. Any behaviour like that is unacceptable and I think it's important for him to learn this. Society as a whole don't accept violence etc.. It would be awful him having to learn the hard way. If that could be avoided and he could be taught this now, it would benefit him in the long run.
Hellion, I must say although I personally don't have experience of working with anyone who's autistic, a good friend and also a relative do. They work in a school for those with autism, Aspergers, downs etc and I know they've encountered quite a few violent episodes with the pupils. As far as I'm aware, those with Aspergers and autism can find it difficult to grasp emotions, they find it difficult to read how others are feeling and I think they struggle with their own emotions. Of course, there's a whole spectrum so it would depend on how severe one suffered with it.

To the OP, does your brother get any help? Do your parents help? Are they aware of your feelings? Sometimes when other family members have difficulties yours get overlooked because everyone is concentrating so hard on helping the other person who's difficulty if apparent. If yours isn't obvious, like you don't have the same outbursts your brother does, then they might not even realise you're suffering too unless you've told them.