A parent remarked that, although she did not want to change her young autistic son's basic identity, she would be happy to have a "cure" for his rages.
I responded (in part):
Sometimes I think it is the hope for a "cure" (an instantaneous "taking away" of problems) that keeps some parents focused away from understanding the reality of their autistic kids. They say "He can't talk because he's autistic. That is a tragedy for which we must find a cure." If instead they were studying the child to figure out how he is attempting to communicate, perhaps they could learn to adopt his method and then adapt the method with him over time until it works better for establishing a relationship between the child and the world.
As for rage, that's an old problem of mine. Nobody could "cure" me of rage. it was something I had to learn on my own. (Sometimes, as the saying goes, the only way around a problem is to go through it. All the way. No matter how long it takes.) I might have learned my way out of repeatedly getting "stuck" in rage if I had been offered a range of ways to handle it. My parents were wonderful, period. But in this respect, I think they lacked the information (about autism) that would have made them better able to help me (in this regard). They taught me why hurting people was wrong, and that helped because at least I learned not to direct my anger against people.
It wasn't until I was fully adult, however, that I learned how I could choose to react in a different way to situations that set off my "rage reaction." I learned that after I realized how much damage the rage was doing to me (physically; it is an extremely high-stress emotion), which motivated me to change.
Your son is very young still. Perhaps all that can be done right now (aside from continuing to help him understand why he does not want to hurt people) is to notice and analyze and eliminate/reduce the factors that cause rage -- and, as it seems possible, offer him alternate ways to react to those enragements that remain.
In response to an example where the child raged because his father did not respond immediately to the child's wish for attention, I wrote:
When I was his age, it hadn't occurred to me that my parents didn't always know what I was thinking and feeling. You do anticipate his need so much (because you are adults and his parents and you love him and therefore are paying attention) that it isn't surprising if he assumes your occasional failure to know his wants is due to a failing on your part.
You probably know that some "experts" think the "core deficit" of autism is "theory of mind deficit" (e.g., an autistic not realizing that other people's inner experience is not the same as his). Your son may not be able to tell the difference between the times when you do know what he wants (because you can read his body language, for instance, or because you have analyzed the situation very quickly) and the times when you do not know what he wants.
I was much (much!) older than your son when I went through a mourning period for my lost assumption that my mother would always respond to my feelings. In fact, of course, she could respond only to the feelings she knew about, and that meant (more and more as I got older) only the feelings I told her about.