Maybe this type of "comedy" is beyond me, after "my time" but I don't get it.
Is it supposed to be funny? And I don't understand the premise. The way it's presented it looks like a hidden-camera situation where they just have this guy there doing absurd things and taping peoples' reactions. But some of the situations seem contrived and reactions from people seems... Ingenuine.
So what's the deal with these movies?
The premise is that comedian Sasha Baron Cohen adopts a persona that exemplifies all of the stereotypes that people have about a certain group -- in the case of Borat, all of the stereotypes Americans and Britons have about people from the developing world; in the case of Bruno, all of the stereotypes Americans and Britons have about gay people (with a bit of European stereotypes thrown in for good measure) -- and to then target individuals likely to react in a bigoted manner towards those groups by interacting with them and provoking them using those stereotypes.
It's a way of exposing their inner bigotry and therefore of making fun of bigots.