It's difficult to believe that even in these highly irrational times there is a need for people and even sovereign nations or institutions like the Vatican to condemn stoning. The need exists, of course, because people and even sovereign nations (one in particular) believe we must, under certain circumstances, be stoned. That is also difficult to believe.
It can be argued, of course, that those people or nations who feel the death penalty is applicable in certain cases have no business condemning the manner in which that penalty is imposed. But the counter-argument that the death penalty should be applied only in cases of extreme misconduct (which does not include adultery), and when applied should not be carried out in such a manner as to assure the process is particularly painful and drawn out, seems an effective riposte--for those committed to the death penalty, in any case.
The practice of stoning seems to be one developed if not popularized during the Bronze Age, where we humans for various reasons developed certain practices and beliefs which plague us to this day. I know too little of Islam or, if you wish, extreme versions of it, to state whether it is believed in this case that stoning is one of those punishments claimed to have been cheerfully imposed by the Deity. I know stoning was practiced by the ancient Jews, if the Bible is any guide; we all know that it was suggested that he who is without sin should throw the first stone. It is possible that stoning is not the cruelest death ever devised by our clever species. The Romans crucified, and it's difficult to imagine a worse death. Still, stoning may be the cruelest of deaths being imposed by the righteous these days.
I haven't heard of anyone taking the position of the cultural relativists in this debate. But surely there must be someone, perhaps some academic or student of an academic, somewhere, who would if pressed assert that this is one of those customs which we cannot judge as right or wrong, being irretrievably guided by prejudices imposed on us for which there is no real justification (there being, of course, no such thing as justification in any real sense--not that anything is real).
This kind of response just doesn't sit well, though. I feel it doesn't because there are certain things which we find repulsive when we are thinking. That is to say, when we are not in a state where it is believed that thinking is improper for some reason--because, e.g., God has done that already and come to certain absolute conclusions which cannot be questioned but must simply be imposed. When we question, we think. When we think, we wonder whether something is fair or appropriate. We may even wonder whether God would want someone stoned or burned.
This is the kind of thing which makes me wonder whether the "New Atheists" as they are called are right, and religion is something to be condemned and eradicated. But that would be to accept an absolute conclusion as well; that one cannot be religious and thoughtful. And it seems apparent that there have been those who were "religious" and still thought, and having thought could not accept that there is some implacable Deity which requires that we be cruel to one another in certain circumstances. Some of these people are still around today, and they are not to be scorned.