BET (officially stands for Black Entertainment Television; or according to The Boondocks, Black Evil Television) is an American television network that airs programming aimed at African American audiences. It was launched in 1980, and was purchased by Viacom in 2001.
Aaron McGruder, creator of The Boondocks comic strip and TV series, is a very vocal opponent of BET, which he blames for dumbing down black people and their pop culture. Both the comics and the show have frequently made scathing comments and jokes at BET's expense, which culminated with two controversial episodes at the end of Season 2 ("The Hunger Strike" and "The Uncle Ruckus Reality Show") that were actually banned from Adult Swim because of legal threats from BET.
Huey Freeman and Michael Caesar frequently complained about the poor quality of BET's programming (and African American media in general). BET has been depicted as a negative influence on the mind of Riley Freeman, and to a lesser extent Cindy McPhearson.
BET was first mentioned in "Return of the King", while Martin Luther King Jr. is ranting about how far downhill the black community has gone, he proclaims that "Black Entertainment Television is the worst thing I have ever seen!". This was part of a longer speech about how disgusted he is with many black people for acting like stereotypical "n***as".
Later in "Riley Wuz Here", Huey decides to conduct an experiment in which he only watches "black TV shows" (implied to be mostly from BET), in order to find out if it really can make one dumber or kill them. After marathoning black television for several days straight, Huey finds that he has become very forgetful and unfocused (though of course, he was doing nothing else besides watching TV at home all day long).
BET becomes the focus of a two-part story arc at the end of the season ("The Hunger Strike" and "The Uncle Ruckus Reality Show"), where it is depicted as being run by an evil supervillainess named Deborah Leevil (a parody of the real BET CEO Debra L. Lee), and her second-in-command Wedgie Rudlin (a parody of the real BET President Reginald Hudlin, who was also a former producer of The Boondocks). Leevil and Rudlin outright say that they hate their own race, and plan to use BET's stupefying shows to "destroy black people".
In "The Hunger Strike", Huey Freeman decides to launch a protest campaign against BET. He goes on a hunger strike (voluntarily fasting/starving himself), while calling for a boycott of BET until the channel is taken off the air. Huey receives the assistance of professional activist Rollo Goodlove, who makes the BET boycott go public. But not only does the boycott prove ineffective against BET's evil plans, it ends with irony; Rollo is offered to have his own sitcom on BET.
In "The Uncle Ruckus Reality Show", Wedgie Rudlin is given the task of producing a new reality show starring Uncle Ruckus, the racist black man who hates other black people. Things are going well until Ruckus learns through a DNA test that he is not really a white man, but was in fact black all along. He becomes so depressed by this revelation that he tries (and fails) to commit suicide. As there can't be a show without a living and functional Ruckus, Wedgie kidnaps the geneticist and forces him to "correct" the DNA test, so that Ruckus could snap back to his old self.