I'll certainly allow that people can be too eager to ignore the existence of the first reason, but it's way too convenient to equally dismiss the possibility of a second reason, or to suggest that such second reasons have already disappeared. Take, for example, this very discussion, which has seen a lot of resentment at positive discrimination. That's a real resentment that exists, whether or not positive discrimination existed or was responsible for a person getting their job, or their place on a show, etc. That's also a barrier: if the default assumption among many is that somebody was the beneficiary of positive discrimination, then they can often feel an extra pressure to prove otherwise.
I'm also surprised that anyone could think that such barriers are entirely removed by simply putting a message to that effect on the application form. Life isn't that simple.