perhaps i'm reading it wrong, but seems to me he's being sarcastic when saying"the smartest people will short"... that if the rest of the world keeps pushing the price higher, these "smart people" in their short positions will get squeezed...
the potential upside seems unlimited, the potential downside is only 100% but if you leverage short, your potential losses are seemingly unlimited... risky position to take perhaps
I am not so sure. Great investors usually drive the market, they have great money and they usually have the best timing. If they short-sell, trend follower can increase price spike and trigger a great drop