An unsustainable price of bitcoin will lead to the collapse of other exchanges since people cashing out on these exchanges requires enormous amount of real money.
This will create a situation where the price of bitcoin in Bitfinex is higher than other exchanges by a big gap. This is not the case, actually the opposite is true: Bitstamp, Gdax, and Gemini prices where higher for substantial durations in the last few weeks.
You can only artificially pump the price to an unsustainable high for a very short period of time (2013/mtgox) or have this market restricted (no withdrawals/deposits, etc...). However, this is not the case. You can withdraw/deposit to bitfinex and their coldwallet shows 1.6bn usd worth of bitcoins.
TL;DR: The author fits the "butt-hurt" category, refuses to accept the reality and tries to find non-real argument for his hypothetical flash crash.
Disclosure: I currently hold no Bitcoin but some bitcoin cash positions. I also think the market is in a bubble. But a bubble with real people dollars flowing in.