Sleight of Hand on IQ

http://news.yahoo.com/texas-executes-man-despite-claims-low-iq-233932865.html

It's always amusing how convoluted the rules are for a good SWPL regarding the whole IQ thing.  It's supposed to not matter per their official rules, but they're obsessed with it---see all the constant articles they're linking to each other about how they're smarter than conservatives or how GW Bush has a low IQ.

But when it comes to denying the moral agency of those with low IQ for purposes of getting them off the death penalty, IQ is suddenly handed down on stone tablets from Heaven Above.

Frankly I find this denial of moral agency pretty offensive---especially when one cuts it at a mere 70..barely a Standard deviation below the US black mean and less exceptional than that in many African countries.  And, if we do deny him moral agency, and the lack of agency isn't temporary or repairable---is that not basically calling him a mad dog, or perhaps a rogue primate?  In such a case wouldn't we just put him down like said dog?  It strikes me as odd that the denial of the Imago Dei would be used as an argument for clemency.  My position is that it is far more dangerous to err on the side of denying moral agency than it is to attribute said agency in error.