I was just like your son.
I have always been a victim of bullying in every form possible, and it's quite annoying.
I was diagnosed with AS in the 5th grade though, and ever since then, my family and I have been working on ironing out some of the worse kinks that come with autism.
I'm 19 now, and I have very few visible outward signs of it.
However, the bullying will never end - that's a fact. You now know why, and you can formulate a plan of attack to ease it. Your son will become a better person because of it, too. At least, that's how I feel.