Of course we can, no secret again if china is the largest owner of the bitcoin, many forums which states they unite for get the benefit of the price of the bitcoin.
Well it's worrying but it's possible China can manipulate the prices single handed due to their stake in the Bitcoin mining network and the amount of Bitcoin owners and bitcoins in their possession. The prices are generally regulated by demand and supply and since they have more in their possession they can either creat a demand (by refusing to sell) or create an abundance of supply.
But that will require the collaboration and coordination of thousands of individuals and organization, I think it it is way more likely that just a few big whales are the ones trying to manipulate the price of bitcoin since that is way easier to coordinate than many individuals.
It's either a small group of whales are manipulating the price because it's hard to make a bigger group that would cooperate in manipulating the price.
Although I don't know who really are manipulating the price but I believe it's happening because the price movement is not normal anymore, one time it will pump and the next thing will happen is dump.