Entertainment represents, what, one-seventh of the US economy? It’s a stretch, but if the agency considers illegal downloads and piracy of films as acts endangering that major economic sector, then it will argue that the US is under economic attack and claim jurisdiction. If they can put something like this across to the American public, as Hoover did for the FBI in the early 1930’s by sensationalizing the exploits of a few local and regional criminal gangs, Homeland Security stands to gain by becoming better funded and better armed (with more and more rights-intrusive laws, electronic surveillance, and sophisticated military weaponry) within the government and against the civilian population.
This is perpetrated most energetically by law-and-order, small-government/non-intrusion politicians growing the ever-increasing law enforcement sector (The creeping privatization of which means valuable contracts) of same government with the collusion of this very stupid population which bent over oh so invitingly for the insertion of the Patriot Act in the first place.
You can damn near do anything with a populace that pays more attention to their votes for TV entertainers and Facebook “Likes” than they do the people who are supposed to represent them in their government.