Some serious missteps here by McCord Adams in this philosophy-oriented article, and not only from a biblical perspective, but even in reading other authors well.
From a historical point of view, it is understandable how Anselm could have come to hold such a principle. Anselm was a member of feudal society in which the amount of honour due to serfs as opposed to lesser nobles, and to lesser nobles as opposed to the king, was very important in dictating behaviour. In fact, somewhat earlier in Anglo-Saxon society, there had been an institution of wergild, according to which the value of a noble, and the wergild of a noble was less that that of a king. If someone killed another person, he was legally obliged to pay the wergild of the one he had killed [precisely like in the Bible!]. on this system, someone might be able to afford to kill a serf, but not a noble, or a noble but not a king. How much one owed for killing a person was thus proportional to the honour accorded to his place in society. So in Anglo-Saxon society, at least for the offence of killing, guilt was proportional to the augustness or majesty of the offended party and not just to the act of offence. But if history makes Anselm’s alleged adherence to the principle understandable, it does nothing to make it more commendable. Indeed, it seems the height of immorality to suppose that the amount of guilt incurred in killing another person depends on the dead man’s social status.
The question is, is it true that to will it is as bad as to do it? It is a part of Christian doctrine that not only one’s actions but also ones’ desires, intentions, and attitudes can render one morally reprehensible. And it is initially plausible to reason that if one genuinely wants to perform an evil action and even tries to perform it, but is unsuccessful because of circumstances beyond his control, he is just as morally culpable as if he had succeeded in performing the act. Suppose Jones tries to shoot Smith, but when he pulls the trigger, the mechanism fails and the gun does not go off. We are strongly inclined to say that Jones is not less morally reprehensible for having failed to kill Smith than he would have been had he succeeded. Yet, if the will often makes one as morally reprehensible as the deed, we would not ordinarily suppose that it makes one as liable to punishment.