He DID admit it to Dawn, when she told him, right before Tribal Council that night, to not make an emotional decision, and he said "Well, I'm an emotional guy"
Of course he said he was afraid of the purple rock! If you're sitting in front of a jury, what argument to flipping sounds better? "Oh, I flipped because you guys were a bunch of a**holes" or "I flipped because I'm a huge fan of Survivor, and I wanted to take the game in my own hands, instead of leaving it up to rocks."