I have nothing against killing murderers as "an eye for an eye". Again, the problem is innocent people do not deserve to die for murders they never commited. To kill the deserving is to accept we kill the undeserving.
To free the deserving is to accept that they will go on to kill the undeserving.
Personally I think I am at more risk of a freed killer, having served his time, than of the State arresting me and executing me unjustly.