There are many here on FR who do believe that the FBI does not abuse it’s powers.
Their cognitive functions seem largely dependent upon what party occupies the White House.
I am one of those. I do believe that individual agents have abused their powers, but since Hoover I feel they have gone out of their way - at the expense of good agents' careers - to prevent themselves from being viewed negatively... "PC gone wild" is one way I've heard it described.
The agents I know are good people. I imagine that any organization is bound to have their stars (psssst, and turds).