Rep. Peter King will hold hearings on “the radicalization” of American Muslims when he gets his gavel for the House’s homeland-security committee. Framing the question that way predetermines its outcome: millions of Americans will be presumptively guilty of drifting into fellow-traveling with al-Qaeda. But King is right that even a statistically miniscule rise in homegrown terrorism deserves thorough analysis. The question is how real King will allow his hearings to get.