"The Secret Meeting That Changed Rap Music and Destroyed a Generation" is one of the more pernicious myths in hip-hop history. The story discusses a meeting held in 1991 between "industry insiders" who had invested in private prisons, and decided that gangster rap would be the perfect style of music to promote criminal culture and shunt the country's youth into prisons—thus leading to greater profits.
The worst part about this myth is that it propogates the notion that our current incarceration rates—which are completely out of control and higher than any other country in the world today—are the result of the culture of those incarcerated, rather than a systemic effort to contain an entire class of citizens. Our exploding prison system doesn't need a conspiracy to operate; it works out in the open, and it's called the War on Drugs. For more on the American Prison system, you're better off reading The New Jim Crow: Mass Incarceration in the Age of Colorblindness than some extremely suspicious internet rumor.