I didn't know what to do other than sit him down and tell him "that is not nice" ...
Regular moms tell me "that's normal " or " he is a boy" I don't feel that way
He also likes to step on bugs...I explained they are alive and that they hurt and he sees me taking bugs outside gently, but he splat them as soon as he sees one...
I think talking about feelings to build empathy should help over time.
This can be in response to the type of situations you've mentioned (maybe a little while after they happen -- we have good talks in the car or at dinner), or they could also be positive examples. "You shared that toy with her. How do you think that makes her feel?" In general, just talk more about how his actions (or yours, or anyone's) affect other people. Repeat 3 million times.
Regarding the laughing at other people's misfortune. It may not be that he actually thinks its funny. Many children that age struggle with how to react when they feel uncomfortable, and one of the things some do is laugh. I think the laughter is an attempt to make the uncomfortable situation go away: "Hey, come on, let's get back to that happy place" and because the world doesn't exist separately from them yet, if they laugh, the world is laughing.
You might try and see what kind of response you get when you talk with him about it later and ask something like, "When Joey got in trouble, did you feel worried?" (or scared or shy or whatever feeling word he has for being anxious). If he responds in a way that indicates that he was feeling uncomfortable, then just validate how it is a little scary when someone else is getting in trouble. And suggest an alternative way of handling the situation (which I don't have any good ideas about at the moment).
I know that as an adult, when someone gets in trouble, say for example a coworker is "talked to" by the supervisor in my presence, I feel pretty embarrassed and uncomfortable. I look at the floor, pretend to be interested in something else, etc. Really its not very respectful of the child to discipline them in front of an audience anyway, but I know it happens to children a lot in our culture, and it kind of makes everyone feel uncomfortable.