How expensive would it be to buy a Browning M-2 .50 cal, mount it behind some armor, and man it with some electro-optical/night vision devices? Probably a fraction of the cost of your “non-lethal” politically correct alternative here.
These pirates don’t understand anything but death when it comes to deterring them. I say give it to them liberally and pile their heads on their home land beach.
http://www.youtube.com/watch?v=HfXLEURxozc&feature=related
Scaring them away to fight another day is no solution...
Here are some more permanent solutions to your pirate problems...