The world is full of fine lines... grey areas as it were. There is very little that can be colored starkly black or white. There is a fine line between an assasin and a bounty hunter. Both kill for money. One mans good is another mans evil. Everyone deserves to die for something.... some more than others. Firth didn't worry too much about the whys. If the price was right, the target was good as dead. Let the gods separate the guilty from the innocent at judgement day. But you had to be alive to spend your bounty.