Jamie Dimon has been talking down bitcoin very harshly lately along with quite a few others in what some have said is a coordinated campaign against bitcoin and other cryptocurrencies. MSNBC recently did an article in which the reporter talking about bitcoin was in a casino setting during the report and appeared to be gambling with poker chips. That was the image MSNBC wanted to attach to bitcoin, apparently. Also, an investor I had never heard of called bitcoin "garbage" and that somehow made the news.
In the case of JP Morgan, it is particularly strange that the company is working on developing its own blockchain while their CEO called bitcoin a "fraud".
Fraud is saying something that isn't true in order to trick someone into giving you their money or otherwise giving you a benefit at their expense. I don't know if JP Morgan used the downturn in the price of bitcoin that followed his statements to buy in, but if they did, that would be ironic. It's the kind of thing that is illegal if you do it with publicly traded stocks or other investments.
Since the Winkelvoss twins were denied permission by the US regulators (the SEC) to have an exchange traded fund that specialized in bitcoin there are no derivatives of bitcoin that are considered publicly traded securities in the US. But in Sweden, there are securities like that which are derivatives of bitcoin. For that reason, a complaint has been filed against Jamie Dimon, CEO of JP Morgan alleging that when he called bitcoin a "fraud" and the market price of bitcoin dropped, apparently in response, this was market manipulation.
Here is where I read the report:
https://www.rt.com/business/404216-jamie-dimon-bitcoin-market-manipulation/