Hosting secret prisons in a foreign country usually means illegal practices. Tax payers have the right to know how their hard-earned money gets spent and where it goes, especially with recent news from the past years show that some of this money goes to fund illegal activities by security institutions such as the CIA and NSA. Transparency has always been one of the fundamental factors that prevent any corruption or illegal activities from taking place.
The power involved with anonymity can very easily be abused. Much the same way the NSA could potentially be abused. The CIA doesn't have enough transparency and probably needs to be reformed. The current state could invite a lot of corruption and misdeeds. Things that can potentially hurt both the US citizens and violate their rights.
There have been rumors about CIA black-sites and secret prisons in foreign countries for several years. The CIA and the United States government have always been very closed mouth when it comes to such allegations. However, the CIA serves the citizens of the United States. Therefore, the agency should be more open about some of its activities; especially activities that might be illegal, or go against American standards.
The CIA may not always do the right thing, but in order for it to be able to operate properly it has to be able to keep secrets. If the CIA was more transparent there would be many people who would be in danger, including CIA operatives all over the world.