No one's innocent, there are only different degrees of responsibility

Recently, I happened to start reading the Millennium trilogy by Stieg Larsson. The second part called 'The Girl who played with Fire' had an interesting caption. Well not so much a caption, as an extract from the book. It said- 'No one is innocent, there are only different degrees of responsibility'.
At first look it sounded as though the writer was making a claim that there really are no innocents in this world & almost everyone at one point or the other has committed a crime. That really did not seem appealing.
But as I thought over the statement, it did strike me as being true. Not in the sense that I had understood it before but in a totally different light. Yes, the writer was correct to an extent in making that claim. When it actually comes down to analyse actions committed by various individuals, then it becomes difficult to measure them all using a single yard stick.
When, for an instance we consider a civilian v/s a person in armed forces, we cannot and do not condemn an armed force officer when he shoots some one down acting according to his role i.e. to protect the society, but when the same civilian takes up arms, its a different story altogether. This all comes down to the fact that both these groups of people have different responsibilities. It is just that an ordinary man i.e our aam aadmi, does not take up the responsibility that he's not accountable for those actions. So in other words, he only seems innocent because he does not hold that responsibility.
How then can we justify this statement when we talk bout the violence in the society? The miscreants who take up arms, take law into their hands and to what end? To start a vicious circle of violence to which there seems to be no end. This is in no way, taking up responsibility but defying the rules of society and misuse of what could have been responsibility to do something good for the society.