Do you honestly believe that Warren is trying to deceive you into investing in productive assets rather than a shiny metal because he wants to manipulate the market?
I believe that his speculation argument against gold holds for the stock market as well. Investors create feedback loops when they buy stocks that then creates even more demand. Buffet believes in the S&P and so he will naturally encourage others to do so.
The value of anything can be propped up by speculation, what varies is the value which can be maintained without speculation (e.g., in cases where the bubble bursts).
I think this is the use of discriminating among (A) resources reasonably expected to decline in value, (B) resources expected to 'hold value' modulo speculation, (C) resources expected to have ongoing returns with or without speculation.
