Yes. I believe him. I think that almost everyone believes that what they are doing is good... or at least correct. When a person rationalizes their actions so many times, they convince them selves that their wrong actions are correct. Take this example from this quote by Al Capone.
"All I ever did was sell beer and whiskey to our best people. All I ever did was to supply a demand that was pretty popular." There is rationalization going on all over the place here. Clearly he thought what he was doing was good. People have to think their actions are correct before going through with them no matter how far they have to strain logic.