The first is that if your goal is to become a professor and you are not accepted with a scholarship into a top-20 political science program, I would not in good conscience recommend that you get a PhD.
Most of the professoriate in international relations comes from the elite schools. Whether this is because these schools function as a prestige cartel or not is immaterial: the reason will not change the current realities. The academic job market is brutal; getting an academic job without a degree from a top-20 institution is even more brutal.I applaud him for his honesty.
(The whole article is good, and a reflection of what I should be doing here more often.)