Are these your allies?
Mark Shea posted a couple days ago, once again reasoning that if you still hold to the Church's traditional approach to capital punishment, then your allies are the likes of barbaric Muslim societies and Communist tyrannies. He even included a cute graph like the one above (I deliberately used a different graph that outlined the world's countries a little better).
If you look at the above chart, there is quite a variety of countries without and with the death penalty. Look carefully. Yes, most Muslim countries have it, so does China. But so does Brazil. So does Japan. So does India. Argentina. Mongolia. I'm not sure there's any trend I can spot there.
Those that have abolished the death penalty? Secular Turkey in the Muslim world. Nepal. Mostly countries aligned with post-Christian Europe. S. America has the death penalty, as well as liberal abortion laws and progress views on gay marriage. Russia has the death penalty, loose abortion laws, and right now no move to recognize gay marriage. Europe, which seems to be the go to reference point for those who wish to abolish the death penalty altogether, is a living, breathing example of post-Christian values: gay marriages, abortion for the longest time, several moving toward legalizing assisted suicide and euthanasia.
I thought of this as yet one more country that banned the death penalty embraces gay marriage. And let's not forget, the United States that brought us federally supported abortion rights was, at the time, also attempting its first round of banning the death penalty. My point is, it's an incredibly weak, almost ludicrous argument. Most of my life I opposed the death penalty outright, though I knew that brought a few problems. I was happy to embrace the Church's (then) teaching that it should be rare in deference to mercy if at all possible, but not if it compromises the ability to protect widows and orphans.
But now, many leaders in the Church, leaning heavily on the State's new-found ability to prevent crime, are seeking to abolish the death penalty altogether. And in lieu of a better reason, apparently some have sought to find reasons of their own to do so, including guilt by association. Looking at the map above, it's easy to see why 'if you support the death penalty, then you're in the camp of barbarism' is really no better than 'because now the State can prevent crime.' We'll have to do better than either of those to justify jettisoning a 2000 year old consistent teaching.