But they haven't shut down bitcoin, almost makes you consider that the NSA has a back door into bitcoin, as has been speculated in the past.
I would argue that Bitcoin is too big for them to shutdown. They cannot explicitly try to shut down Bitcoin companies because they will be hauled over the coals in courts. The pressure would be subtle - difficulties in dealing with banks, cumbersome compliance procedures, extensive record-keeping requirements. If you look at the BitLicense being proposed, you know that times are going to change.