The point is simple: off-topic content is far easier to submit than good content. There's way more of it, and it's of interest to far more people. It would be very simple, were there no controls, to crowd out "good" content with politics/pics/etc... Which means that doing the opposite: crowding out bad content with good content, is very difficult. It would require a significant amount of work to go find and promote good articles, as compared to "bad" ones.

If anyone actually thinks this isn't so, think about the mental effort and learning required to write a good article about monads vs the effort required to rant about Bush or Obama or post a cool/funny pic.

("good" and "bad" are simplistic. I actually thought this article was kind of interesting; I just don't think it belongs here)