It was suspiciously warm, the reception given to a study published a week ago in the Journal of Sexual Medicine. A survey of 4,600 young people in the Netherlands, aged 15 to 25, found the behavioral impact of pornography—most of it online now—to be surprisingly small. Reaction to the news? People didn't whoop exactly. But you know they wanted to.

Pundits loved the contrarian view, parents loved being let off the hook. Of course, to the study's author, who said "previous studies could have overestimated the association...