The Bolsheviks grossly abused imprisonment as well; should Christians oppose the confinement of criminals?
Europeans oppose the death penalty because it reminds them of the gross abuse of the death penalty that permeated their continent for millenia. This is the continent that produced trial by ordeal, drawing and quartering, burning at the stake, Reign of Terror, Holocaust and Great Purge. Furthermore, these tactics were used not simply to rid society of murderers, but also of petty poor criminals, the undesirable, and religious and political enemies of all sorts.
In America, one has to go back to the 1600's to find state sanctioned death penalty abuse akin to what was a normal feature of European life. Not even the leaders of the Confederacy faced the noose.
I was indicating that a very profound Christian view for opposing capital punishment was given by Nicolai Berdyaev. I could not do justice to them by giving an oversimplified paraphrase of them. You may want to read them for yourselves. His views have relevance to the modern era precisely because of his experience in the Soviet Union and the very REAL (not abstract) issues of life and death which millions confronted for decades. Incidentally, my reference to the "Thou shalt not kill..." commandment and what all biblical scholars now realize relative to the same is that in the primitive Jewish faith community it meant, in effect, " thou shall not kill another member of the covenant community". But volumes have been written about that. Suffice it to say it's NOT some kind of modern prohibition of capital punishment.