if ordinary people did not agree to do these barbaric acts, they just wouldn't happen. dick cheney or whoever wouldn't do it on his own.some people continue to agree to perform whatever inhumane acts of torture they are told to. (leaving aside the milgram stuff) seriously - who are the people who would do that, nobody is forced to join these 'special forces' or the CIA. presumably they get some enjoyment out of the job - is it the case that the more extreme is your sadism the better you are at the work? such criminal tendency should be enough of a character flaw to disqualify them from any respectable employment.
'it's a dirty job but someone has to do it' - no, they don't