If you understand that they are entirely corrupt and serve only jews then there is no valid argument. However, if you were to argue with a normie you would need to overcome the following objections. The FBI is necessary to police potentially corrupt local governments. They are the ones who can investigate politicians. Assuming they weren't corrupt, that would be an extremely important task. They are also the ones who have nation wide jurisdiction which is necessary for investigating and fighting interstate crime, and crime syndicates. The CIA, if they weren't corrupt, would be an important intelligence gathering institution. Obviously the same can be done by any organization with a different name, or even the military; but in theory they are specialists is covert intelligence gathering.