Food Inc. director Robert KennerRobert Kenner never set out to make a terrifying film when he started Food, Inc. But along the way, he found the food industry to be stunningly secretive--and what it's hiding to be downright scary. The film shines a bright light on the handful of corporations that, behind a cloak of glitzy marketing campaigns, do the dirty work of putting cheap food on our plates. As Variety put it, the film "does for the supermarket what Jaws did for the beach." Not long after the film opened nationwide, I caught up with Kenner by phone from …