As the article said : I have ETF shorting the index, Shorting with a x5 leveraged, I have ETF on gold, oil, bonds, whatever I can think of, all less correlated to equity than any active fund. Probably those ETF trade for far less volume than S&P's ETF but I dont get how The 1st dude (the 2008 short guy) can pretend their is a systematic risk with ETF when he only address the (legitimate) risk of If he only mean we have an irrational equity bull market because of ETF (which are mostly S&P related, volume wise), then he got a point. But it's not "passive is a bublle" it must say "passive is creating the bubble'"and active or passive, you'd better stay away of that artificial bull market"self-reinforcing feedback loop"
of equity's ETF and ignore the ton of others ETF which counter the feedback.