If there was a conscious effort to install a caste system then Micheal Vick would have led his team to a superbowl win, as would have McNabb. There would be no Peyton Hillis or Danny Woodhead. Things would be much worse if the whole thing was orchestrated. As it is the system is voluntary and held in place by the slow changing attitudes of fans and the apathy of the media to call attention to it.
Don's post explained it all in very clear fashion, it is worth reading again...
"It's not a conspiracy; rather it's political correctness, or more appropriately, Cultural Marxism at work. Cultural Marxist ideology maintains that blacks are superior athletes to Whites, and that they will effortlessly dominate any sport they are "interested" in. They are "interested" in football and basketball and have talent for those two sports, so organized football and basketball, beginning in the late 1960s when the Permanent Cultural Marxist Revolution began in earnest, slowly institutionalized black dominance in football and basketball, with no small assistance from the media's positive reinforcement of the trends. The unwritten rules the NFL abides by have been codified over time, and no one is going to violate them other than by very stealthy, piecemeal methods, because to do so openly is a lose-lose situation. And very few have any interest in "violating" them anyway, any more than the generals who work their way up through the military are going to speak out against their Commander in Chief, or U.S. foreign policy.
The football (and basketball) scouts, coaches, executives, broadcasters, etc., have been richly rewarded by being good soldiers and playing successfully by the unwritten rules. No written directives from the NFL office are necessary, nor are there small groups of owners secretly meeting to decide how many Whites should be "allowed" to play wide receiver. It's just the way the system works; the NFL is no different than any other societal institution or large corporation, other than it's set up to have black dominance in perpetuity while falsely claiming to be "colorblind."