It does not say that someone who did not go to a top school performs more poorly. It does not say that those who did not graduate from a top school are not good enough. All it says is that from a relative starting point, if you graduate from e.g. Harvard, you are more likely to be successful than if you did not.
My nitpicks with this premise are: is success defined in financial terms? Is it in position (CEO vs engineer)? What is the empirical evidence that graduating from a top school confers greater success (I think that there is such data, but citing it would be nice). There's enough stuff here to talk about that I am somewhat flabbergasted that you took this as a personal affront and misconstrue what's actually being talked about.