Ryan is right, it is a matter of psychology and the powerless 'acting out' to demonstrate control in their lives. Thus, white teenagers in Transformers wouldn't shut the fuck up, greasy nerd guy in Harry Potter felt the need to yell out various gems such as "GET SOME, HARRY!" when he was kissing his girl-interest and "TAKE EM OFF, PEOPLE!" when the 3d section of the movie war over.. and yeah, the black community tends to have a general issue with yelling shit in the movies, but that speaks to the general powerlessness of the community (broad-brushing, obviously).

I submit that it isn't necessarily that folks are of a particular culture / heritage in and of itself, but it is the lack of control in their lives that has the psychological 'acting out' result.

But, understanding why something is doesn't necessarily make it any less annoying, no.