I received a call from the school counselor when my youngest was in second grade letting me know that the school was very sorry for the bullying situation my son had been experiencing and that she was working with both my son and his classmate to resolve the situation. She seemed shocked when I told her I knew nothing about it. My son never once complained, talked about this boy as a friend, and didn't see his actions as bullying. It was mostly rough-housing like pushing my son up against the wall and pinning him against the wall, etc., but it was in the context of playing.
I asked my son why it didn't bother him, and he said it didn't make him feel intimidated or afraid - he somewhat saw this kid as an equal, not as someone "over" him. And while my son does not have Asperger's, I do think he has some of the same issues with interpreting other's social cues appropriately and is often blunt and doesn't understand why others react negatively. Despite that, he's well-liked, gets along with most kids, and is a good natured boy.
So we had to sit down with our son and explain boundaries, how to draw boundaries, etc.
I don't have any real useful advice for you - just wanted you to know you're not alone.
