One of the characteristics of my son's autism is that he laughs when he feels sadness or sees pain. He laughs at crying babies. He thinks funerals are hysterical. He was present for his grandmother's late sickness, and he laughed most of the time -- and he dearly loved his Nana. To a casual observer, he looks like a sadist. Knowing him as I do, I see that this isn't sadism at all. His brain has linked up the sadness pathway to laughter. I can't recall a time in the last 15 years where I've seen him cry. or express sadness in any other way.

The young man you slapped may have been a sadist who genuinely enjoyed the pain of the other child. Your emotional reaction would have been appropriate, but as you noted, the slap was not even if the emotional reaction was right. The worse part of the slap is that your emotional reaction may not have been correct. The young man who was laughing may not have been getting a thrill out of the other child's suffering. He may have been laughing for other reasons that don't reveal a terrible motivation.

I used to feel sad for my son given that he doesn't seem to feel the sadness the way the rest of us do. But when I really reflected on it, wouldn't all of us rather laugh during those times? It's not the reaction the outside world wants to see, and those who don't know my son would certainly condemn him for laughing when he should cry, but at this point, I wouldn't wish for him to be any different. When he visits me at my deathbed, I will relish his laughter.