Often times military contractors are used to help fight the US wars. However, these companies allow the US to have a certain blame factor so they can pawn off poor behavior on a separate company. Military contractors should not be allowed in interrogation rooms for the main reason that if something were to go wrong, the US needs to be help personally responsible, not some separate company.
Interrogations and security are very serious matters and by allowing contractors to perform these duties open the door for problems. Government employees are trained to properly handle these situations. Or at least we hope they are, but we have no idea what type of training if any the contractors receive. Plus by handing over these duties we, as a government, are not in charge of the situation. The government is giving up control and allowing the contractors to do as they see fit. There are times and situations where contractors are needed and should be used, but anything involving security or interrogations should be done by government employees only so that we are sure that certain standards wll be followed.