This way the doubt arrives later, gradually, and he pushes it away each time until he can't. He genuinely believes the end, however dirty, can justify the means: not because he's naïve, and not because he's a cold Machiavellian, but because he believes someone has to get their hands dirty for the greater good, since those who could change things cleanly never actually will. Once the act is carried out, then it becomes real, personal, and irrevocable.