That's not remotely true, you're projecting how you would abuse power. Not everyone is as evil-minded, and I hope they continue to do a great job at keeping your ilk out of the organization.
So you have to be evil to think of what evil can do by the statement you made. Can't you see how this leads to a catch-22 situation where if you get rid of anyone that can think of possible evil acts makes your organization blind and therefor at higher risk of actually committing those acts.
Also, when looking at the people we all vote into power, there is a incredible amount of naivety here. Snowden should have keyed you in on what people in power are doing.
People who aren't evil-minded don't go to work for a government organization responsible for constitution-violating surveillance of their fellow citizens.
