Even for Greenpeace, a group known for turning high-seas drama into political statement, the foray into the Nantucket Sound wind farm debate has played like perfect theater. Take, for instance, the picture-postcard morning of Aug. 17, when a pair of Greenpeace motorboats surrounded a schooner crammed with wind farm opponents, including Robert F. Kennedy Jr. It was a made-for-TV face-off that, indeed, was reported on the national news that night. But for Greenpeace, a $360 million organization that spends about $3.3 million each year on U.S. campaigns, ongoing efforts for the Cape Wind project transcend interrupting a Kennedy sail. Today,...