That said, of course there are still things in the text that a decent Christian will have trouble rationalizing. My claim is just that he'll have lot less trouble than a decent Muslim.
I think "decent" is a bit of a distraction here. I would interpret "decency" to refer to ordinary interpersonal morality, rather than ideology. Plenty of decent people believed and believe in the legitimacy of religious coercion. Some of them were saints. However, decent people can be a political or military threat. What we really want is an ideological transformation such that as many Muslims consider liberalism (broadly understood) as consistent with their ancestral faith as Jews or Christians do now.
If we substitute "liberal" for "decent", then we have a supply-side theory of illiberal religious exegesis. There are four kinds of exegesis of the texts: liberal Christian, illiberal Christian, liberal Muslim and illiberal Muslim, all of which exist, but with a negative correlation between liberalism and Islam. Anti-realist's theory is that this is because it is costlier to produce liberal Muslim exegesis (in cognitive dissonance or some other currency) than to accomplish the same trick for Christianity or Buddhism.
The alternative view would be that the greater relative salience of liberalism in Christianity is demand-, rather than supply- driven. On this view, cognitive dissonance is not a great obstacle to the religious beliefs of most people. For non-religious reasons, Christians want more liberal religious beliefs than Muslims do. If the forces making Christendom more liberal act in the Muslim world, they will (and have) increased the demand for liberal exegesis of the Qu'ran.