1) Shorting into a bubble is usually a terrible idea.
2) The only realistic way to short BTC is to do so via a very small list of exchanges. Even if you trust them (which, given the history of cryptocurrency exchanges is hardly a given) the borrow cost is huge: there's no way you could reasonably make this kind of macro BTC bet.
The combination of these two realities makes the "If you don't believe the price, you ought to be shorting it" assertion completely baseless.
2) The only realistic way to short BTC is to do so via a very small list of exchanges. Even if you trust them (which, given the history of cryptocurrency exchanges is hardly a given) the borrow cost is huge: there's no way you could reasonably make this kind of macro BTC bet.
The combination of these two realities makes the "If you don't believe the price, you ought to be shorting it" assertion completely baseless.