There is a reason not all sentences are life sentences. Sometimes people do things wrong and if they are willing to change their ways we as a society should forgive them if it's safely possible. Just because someone does something wrong once doesn't mean they are that person forever.
I can't explain it but every time I hear that phrase I get a very visceral feeling of injustice. The phrase represents extrajudicial punishment by a mob or powerful entity, and the negation of fairness, proportionality, and due process, often expressed by a person who does not care because they are certain that they themselves will not fall victim to abuses of such systems.