The image I saw, that he got the warning about, was an image of an infant circumcision in progress - operating sheet cut-away, showing an infant's penis and testicles, with the foreskin in a clamp about to be cut.
While I agree that we should be able to have an adult discussion of matters such as circumcision I also understand that this site has a rule of no images of minors, at all. Uploading or linking to an image of a minor or part of a minor is not allowed on this site. dx was clearly illustrating a point and there was no dubious sexual intent behind the posting of that image. The mod team, fairly I thought, removed the image and warned him that it was not allowed on this site. He then linked to the same or similar image. That time he knew he was not supposed to - what did he expect the mod team to do?
That image was not a required part of the discussion and even if it was that's just tough - the no images of minors rule is clear.