He’s already told the most “dangerous” information: that US intelligence agencies sweep up and record every phone call and much of the Internet traffic in the US. So now they want to keep him out of the public eye so people don’t think about that or ask questions and to serve as a warning to any other whistle blowers.
Bet he has a lot more to share with the world, He worked for the CIA before he worked for Booz Allen Hamilton. That is probably the big problem.