[gnaritas]

The market itself cannot go to zero, but individual stocks can. If you're of the view the market can't be beat and investing in index funds is the way to go then your position is fine. If you're of the view where you select the stocks you want to invest in, as a great number of market participants are, then your position if flawed because stocks do go to 0 and as such exiting losing stocks makes sense. Tossing all your money into an index fund is not trading, so you're not even talking about the same thing I am.

Flash crashes massively hurt people who invest in particular stocks because they do often have exit points which get triggered by those crashes. The advice you're giving doesn't apply to these people, they're not the ones just dumping everything into an index fund.