Sure this was the line from the movie Gangs of New York. But it seems like it's a very effective tactic for getting things working the way you might want them to work. Keep the poor uneducated and poor, they will do anything for a dollar. Convince them that their neighbor is the enemy, reward them when they comply, and they will take care of the opposition for you. Has this tactic ever been employed? How often? On what scale?
Has this tactic ever been employed?
Romans employed it via Greens vs Blues rivalry.
On a higher level, Divide and Conquer (Divide et impera) is centuries old approach (as the Latin name attests to); and is traced back as far as Philipp II of Macedon (Alexander the Great's father), arguably one of the most capable rulers of not only antiquity but all times. It works just as well on the non-poor as the poor, too.