According to President Harry S Truman, Hoover transformed the FBI into his private secret police force; Truman stated that "we want no Gestapo or secret police. FBI is tending in that direction. They are dabbling in sex-life scandals and plain blackmail... and all congressmen and senators are afraid of him."
In addition, Hoover used the FBI to harass political dissenters and activists, to amass secret files on political leaders, and to collect evidence using illegal methods. Hoover consequently amassed a great deal of power and was in a position to intimidate and threaten sitting Presidents.
The FBI as an institution needs a clean slate and a new symbol of highest ethics, starting with a new building name (and maybe soon, a new building too).