Any time the market crashes, people cry out that it's manipulated.  All markets are "manipulated" to some extent, but usually it's just market forces--buying and selling--in play.  Bitcoin is probably more susceptible to actual manipulation IF the person doing the manipulation has enough money to do it.  If you compare bitcoin to Apple stock, for example, you'd have to do much less buying or selling to move the price, though it's still a lot.  In general, I don't buy it when people claim the market is manipulated.  You hear that quite a bit about precious metals, but there hasn't been great evidence that there's been some sort of coordinated effort to suppress prices (or inflate them).

In addition, I'd agree that bitcoin isn't a stock.  That should be obvious.  But its price does go up and down, very much like a stock price and unlike many currencies.  Yes, there is the cryptography and all of that but ultimately its prone to the market forces of supply and demand, just like a stock is.  That is independent of the nature of crypto, or of what a stock represents.