Sex, Pleasure, Circumcision and Economics
I have no idea how good the evidence is, but it strikes me that there is a serious logical problem with one step in the argument—from less sensitivity to less pleasure. The limiting factor to duration of sexual intercourse, under most circumstances, is male endurance; one can plausibly model the process as a rising intensity of pleasure up to the point of orgasm, with total utility equal to the area under the curve. If so, greater sensitivity simply means that you reach the same maximum sooner, reducing the area under the pleasure curve.
And that's without even considering the utility of the other participant in the process.