In a recent episode, the Freakanomics podcast talks about why you should index. It's a great show - check it out: http://freakonomics.com/podcast/stupidest-money/
Interestingly, Anthony Scaramucci is interviewed as being an advocate of active management (he's the guy who ended up being fired by Trump after 10 days). Scaramucci's arguments for active management don't really make any sense - they are based on the idea that financial advisors and active management are the same thing. They are not. A good financial advisor who understands indexing is well worth the fees. Such an advisor can help in tax planning, retirement, college savings etc and provide real value to clients without ever selling an actively managed product.