Attempts to manipulate Bitcoin price downwards will result in losses for the manipulator due to 24/7 global trading allowing others to buy it cheaply.
"you can't really do that with Bitcoin because if you manipulated it down you would be the loser because people would be buying it cheap you know in Japan and China and Europe while you're asleep and then you're going to wake up and you're going to find that you're naked short and you've lost your shirt"