It is mostly ignorance and superstition among members of congress to believe that destroying the prison will impress anyone in the Arab World who matters. Really shows great weakness.
Many mistakes were made. For example, the US official in charge of prisons decided to work with Ali al-Jabouri, the warden of Abu Ghraib prison, apparently unaware of the prison's fearsome reputation as the place where tens of thousands perished under Saddam Hussein. The coalition rehabilitated Abu Ghraib and today uses it as a prison. The symbolism may be lost on the US administrators but it is not lost on Iraqis.
It's worth reading in its entirety IMHO: How to Get Out of Iraq. It's especially relevant with regard to Torie's comment, BTW.
PS. This was written well before the whole prison abuse scandal broke into the open.