Do you have evidence or arguments to support this naked assertion?
From Index Fund Advisors:
More than a hundred years of academic research points to index funds as an investor's best investment.
They have several recommendations by Nobel laureates on that page, and have a index of papers here. As a general comment, the Efficient Markets Hypothesis is relevant: unless your money manager is insider trading (and if you, as a customer, know about that, then probably so does the SEC), you should not expect them to do significantly better than the market as a whole. The EMH has holes; Buffet has famously outperformed the market and index funds by dint of superior rationality, but most people are not qualified to judge which money managers are rational enough to be better than index funds.
Index Fund Advisors
You don't think they might be a bit, um... biased? :-)
Marketing BS is not evidence.
And before we get into the EMH mess (by the way, how strong a version are you arguing for?) let me ask you, which market? There are a whole bunch of different markets -- what makes large-cap US equity special?
P/S/A: There are single sentences which can create life-changing amounts of difference.