Well, I think there are two kinds of manipulation. First is manipulating the system itself, which is, not possible. At least it was not possible up to today. For example manipulating the transactions, software being used by the network or database directly. It is the most robust digital system we may ever had, a real open blockchain like bitcoin, so in order to manipulate it, one would need to manipulate every point in the decentralized network or turning of the internet, so to say it may not be feasible anymore. thats where it is not attackable, in contrast to centralized systems.
But for sure you can manipulate on top of that, for example buying and or selling big amounts, and try to hurt it like that. Also the big fiat system and organizations or states and goverments benefiting from it, can try to regulate it or make it simply illegal. Some people wouldnt care (because in the end they can just prohibit it but not prevent a transaction to go trough for example), but the majority would, i think.