I appreciate your comment. You are correct in stating/asking "how difficult it is to pick an active manager who will outperform over time." The evidence is clear--it is incredibly difficult. And even if an outperforming manager is picked, it is very difficult to prove that choice was due to skillful selection or just luck.
With regard to the "par" analogy, you are also correct--it is not perfect. I find it to be a simple and memorable one, however, which communicates what I believe to be important: out-performance is so rare (and fleeting when it does occur) that harnessing market returns "wins" over the long haul.