There's clearly humor that goes too far and humor that is violative, and we are engaged in our humor in a complex call-and-response with one another. I'm telling you a joke to see if you think that it's funny... but if one of us violates some principle or touches on a particularly tender spot of the other, normally we adjust to that and move on.

This quote is talking about how humor can be dangerous if it crosses a line in being too offensive, and how people usually adjust to this when it happens. It is saying that when someone tells a joke, they are testing to see if the other person finds it funny. If it goes too far, or is hurtful or offensive to the other person, then the person telling the joke will adjust and they will both move on.