If you truly can consistently beat the market, you are already making a killing with your _own_ money.
If you want to use _my_ money to place your bets (presumably b/c you want to leverage your market beating ability), I want a guarantee (because I'm more than happy to take the return of the index).
Unfortunately no one will agree to this as long as everyone else is willing to invest _and_ shoulder the risk
If you can't beat the market with your own money, you shouldn't be trying to do it with someone else's.
If you can beat the market with your own money, why are you so worried about the downside? There should be little risk for someone who claims to be able to beat the market.
If they say that's too much risk, they likely don't think they can consistently beat the market.