It's probably a phrase I have repeaeted on the AB more than any other - but it bears repeating again - our laws are what make us civilised.
That is why, as a civilised society, we set out a series of punishments, and abide by them, because - with the exception of capital punishment which is barbaric primitive revenge - that is how a civilised society deals with its offenders.
So we don't allow the queue of people who imagine they could 'throw the switch', or 'have ten minutes alone with ...' and similar emotive, but unfounded claims - to carry out what their emotions lead them to think is appropriate retribution.
The system is far from perfect, but it is the best that we have, and we have to accept it, including its limitations.