Why would you assume 'piracy' doesn't refer to actual piracy? It's a fairly big deal in several parts of the world.

Sure, many things are a 'big deal' in some parts of the world - malaria, corrupt governments, famine, domestic violence, ebola, contaminated drinking water, etc etc.

Why did I presume he meant data sharing 'piracy'? Well he didn't choose to mention organised crime, of which naval piracy is a small part. It would probably be a more relevant target for sigint than e.g. Somalis in speedboats, and also more relevant to US security.

The author is, imo, casting around for buzzwords/bogeymen, and he thought data sharing 'piracy' hit the right buttons.

Because you don't need a strong cipher to send text messages like "Yo-ho-ho, and a bottle of rum."

Presumably pirates favor arrrr-C4 or arrrr-SA (both of them invented by Ronald Rivest.)

Well, in absence of tangible success, what else can you do but admit failure, or otherwise produce massive amounts of hot air?

It's probably easier to catch a “pirate” than a “terrorist”, so if the NSA has you believe “piracy” is a threat to National Security, then maybe they can claim some success stories after all.