Maybe laughter is also a way that we repress our sadness/insecurities, in order save face? I cry solemnly when I'm alone when it comes to these things- death of a person/relationship.
Goin off on tangents here:
Some cultures view death as a continuation of life.. Although mourning is important, remembering the good times spent with that person is also another way to keep them alive, and a way to wish them happiness in the afterlife.
I also think that what we see in the media does have a desensitizing effect.. I think the worst thing that can happen to us humans is the effects of media on apathy & how we relate to one another.. The influence of mass communication is so subtle that we don't quite notice it our daily interactions with others.