It's a good counterpoint to the equally throw away argument that "if you disagreed with x you should have shorted it".
The problem with shorting is you can't just be right about the eventual direction... You have to be pretty bang on with the timing as well.
Therefore it's absolutely possible for people to suspect or have strong belief that something is unsustainable without having the liquidity or confidence on timing to take action on it.
No it's not to say there aren't Perma bears and other I told you so people crawling out of the woodwork, but that doesn't mean that every person who didn't capitalize on this is Monday-morning quarterbacking.
