I had not thought of laughter as an emotion - or "emotional release" I should say. I see what you are saying there. Laughter is actually a lot like crying. What you said about it being a coping mechanism is a good point as well and makes a lot of sense. We often do use laughter to cope. Sometimes we even laugh in very inappropriate situations.

I have never heard the joke about Christa McAuliffe's eye color but it sounds like it might be quite distasteful.