Are we to assume that these people who are conditioned to ignore people in crisis correctly apply laughter in most situations?
If someone were to fall off a ladder and is in obvious pain, it's highly unlikely that the person on the scene will be laughing. In fact, it is highly likely that the person who witness the person falling off the ladder will most likely run over to see if the person was hurt or needed any assistance. On the other hand, if someone were to spill his ice cream cone in his lap, that might be seen as funny causing people to laugh.
How exactly do we learn as a society from race inspired humor?
Yes, comedy sometimes can teach us something. Yes, sometimes comedy can open our eyes to something. But, it isn't a necessity that comedy teaches us anything. The first rule of comedy is to make people laugh. I have observed that most standup comics get their material from life. Things in their own lives. Things in other peoples lives. Things in the world. Religion, politics, racism, relationship, pop culture, music, current events, war, things they see on the news, and anything else they may have observed. Having their material inspired by everything in the world (good and bad) is not a bad thing just as long as it's funny. Trust me, if a comic crosses the line in his/her jokes they will most likely suffer negative feedback. There are recent examples of comics suffering public negative feedback due to them crossing the line. There was Monique, Kathy Griffin, Bill Maher, and just a few years ago Michael Richards.
Does it not just cement racist stereotypes?
All black people are good rappers and white people have no rhythm? Really?
Is this kind of stuff "really" funny?
Yes it can be funny depending on all kinds of variables. The context of the joke, the details of the joke, the words and language used in the joke, and so on. On the other hand, it might proved to over the line, in bad taste, and not funny. Depending on the same variables. The context of the joke, the details of the joke, the words and language used in the joke, and so on.