Remember the 2008 subprime mortgage crisis, famously caused by passive investors buying CDOs through their Vanguard funds? Or the dotcom bubble? The great depression? Remember when passive investors were buying tulip ETFs in the 1600s?

You don't, because every single financial bubble in history has been caused by active investors speculating and gambling, in most cases with other people's money. And now that people want to stop giving them money (and the associated fees) they turn around and go "you don't know what you are doing, you'll totally cause a bubble". Give me a break.