What makes us laugh ?

I recently watched the Kajol Ajay starrer "u me aur Hum " . No doubt the movie from the starting till the end was good ... Everthing in the movie from screen play to choreography , from storyline to music was done perfectly and beautifully .
But as i lay in bed after returning from the movie, one question kept recurring to me.
The hilarious scenes ( n especially dailogues) made me think about them over and again .
The dailogues written to makes us laugh indeed left me embarassed and worried.
Most of the small jokes used in the movie were beeped.
The characters shown in the movie were doctors who played such jokes.Are the proffesionals today only educated and not literate? Why dont the dailogue writers display any respect towards the country or towards the language or to the audience watching the movie?
Or are they short of talent that they can make people laugh with only dirty jokes ?
Leave U me aur hum apart ,most indian reality shows are made with no respect towards the country or towards the language.Conversations in them are beeped over and again.
All the foreign channels do conduct reality shows but they have a very good accent towards the game.And inhere anyone could find dirty words coming out of each competetors no matter they are males or females.

This disrespect towards the language is what they call it as the trend and the development.Is it a mark of style ? Does this signify literacy ?Why is the decentcy level or the respect for ones country or language falling with increasing education ?