I will admit that I would not want to be thought of as Mr. Average. Who would? I guess it somewhat depends on what Mr. Average is like -- is he a dull guy who is satisfied with a C grade? I don't think index investors would think of themselves that way. More then likely they would say they were willing to just settle for a B+.
I am going out on a limb and postulating that many "index investors" think of themselves as above average because they are relying on backtest results that say they are likely to beat the stupid money that trades a lot. I'm not saying they are wrong, just that many index investors do not think of themselves as "just average".
Regarding the OP, there is the whole question of "what index"? There are so many indexes out there. Some people trade indexes. And ETF's are just baskets of stocks, why not flip them? That's what many do. Have you guys heard that biotech is hot? Buy a biotech ETF to protect yourself from individual stock risk.
You can probably tell I'm having fun with this.
Please don't take me too seriously (but I'm above average).