Hi fireman00,
While I sympathize with the loss of your friends, the fact remains this argument is an Appeal To Emotion and, as such, has no real merit. If you are going to give a sustained defense as to why state executions should be a defining feature of our society, you'll need to come up with something more enduring than reciprocal vengeance.
I'm fine with reciprocal vengeance
While this may seem like a crass statement on my part, what arguments such as this really boil down to are We Should Have Executions Because It Will Make Us Feel Better. That a policy may seem emotionally self-gratifying does not make it a morally sound policy.
Thank you for taking it upon yourself to be the guardian of morality for the rest of us
Also, as per your last paragraph, life imprisonment would also "permanently remove" a murderer from society. Depending on the nature of their imprisonment, the aforementioned murderer may also be able to contribute to society in some way (such as through prison labor systems).
life imprisonment doesn't permanently remove a murder from society, just changes the society he interacts with.