he didn't say that.
he did say that if some of loaded clients needs money or forces loaded to sell their bitcoin, in the execs of 10 000 BTC, it will take the price down to $400. That does not mean that the price will stay at $400.
Hm, no.
He claimed it makes very little sense to "buy above 400". That only makes sense if there is a substantial *trend* aiming for sub-400 coins.
Take the silk road bust flash crash: price dipped drastically, but that didn't really make a dent in the short term average valuation. In fact, it was the beginning of a huge uptrend (obviously also influenced by China).
Anyway, brief dips to a certain level are unimportant except for a few lucky traders who buy (or the unlucky ones who sell at the bottom).
But talking about "prices that don't make sense" isn't about quick crashes that recover almost immediately, but trends with some amount of staying power.
And, as I said, I see little evidence for a trend that takes us to sub 400 and makes us stay there. Doesn't mean it can't happen, but the evidence so far points towards a range between 500 and 1000 for the near future (dips nonwithstanding)