From American Mercenary:
Claiming moral high ground when you are in the business of killing people seems a dubious exercise in ethics at best. You can quote me on that. But there is a serious bit of ethics that you need to work out for yourself, if you want to be able to live with yourself at the end of the day. Using lethal force is always an ethical decision, and having a proper ethical framework to deal with the aftermath is something you need to put into place.
My bottom line, if you justify your killing as being “for the greater good” you need to shoot yourself next. Fighting for the “greater good” is the justification of tyrants both great and petty.
When you need to justify your actions remember what you are fighting for, which is your own individual liberty and freedom. You don’t need to justify yourself beyond that. Killing those who would oppress you, or aid in your oppression, is a simple act of self defense. And there is no justification needed for protecting yourself. The people who lie to themselves and ascribe grand notions to the justification of their actions usually end up needing chemical support (alcohol, drugs) to keep their brain from shouting the truth back at them and destroying their self worth.