True but most of them do(especially the murderers and rapists). As cruel as that may sound coming from me....
If they're no longer living, then there's zero chance they get out of prison and commit more of these heinous crimes.
Where did you get that statistic? Comparatively few prisoners are murderers or rapists. I'm not saying the people in for burglary, assault, theft, drug crimes, etc are angels, but they don't deserve to die for those crimes. Let them do their time and be released, and we should do everything we can to reduce their recidivism rate once they're out.
Honestly, I am uncomfortable with saying even murderers and rapists should be fair game in prison. The only cases where I unconditionally support the death penalty are mass murderers and serial killers. A single murder could be because of a personal grudge and nothing more, and I believe a sentence to life in prison is a just punishment for that. But when someone kills multiple people, he becomes a betrayer of the species, and must be put down.