Wrong to execute?

I am fed up of abolitionists - often in a Christian guise and misusing Scripture - claiming 'the moral high ground'.
Firstly, please read the following: http://www.dailymail.co.uk/news/article-2074232/Eve-Carson-trial-Kidnapped-UNC-student-president-wanted-pray-murder.html
Secondly, answer this question:
What kind of society can state to its citizenry that no matter what they do or whom they murder - their own lives may never be threatened?

I honestly cannot see any moral base whatsoever to such thinking - to pretend it is Christian borders on blasphemy.