Yes. If someone has committed a crime that is worthy of death it is because they are too dangerous to be allowed out into society ever again and death is the only means we have to assure that.
You are putting other people at risk. That is not acceptable.
Your cute little snuggle bunny killers did not just happen to kill someone by accident. They either killed multiple victims or they killed in hideous ways.
We put murderers in jail ALL THE TIME. Very few of them get the death penalty. Do you think all of them should get the death penalty? Why do you suppose that hasn't happened?