Yeah, I thought it was a little strange everyone was talking about his privates in that particular picture. Nudity does have that effect on people, which is understanding since it's considered "bad," but it's like no one noticed anything else.
I don't know that anyone is considering this particular piece of nudity "bad". One of the chief roles of a monarchical pair was to produce offspring that could keep the dynasty going, and to that end royal genitalia have long been matters of much speculation, some discussion, and occasional examination.
Prior to marriage, prospective queens were often physically examined for suitability to bear children. Regnant queens were often forced to bear children with senior members of the court present in order to bear witness that the child was not exchanged at birth. Queen Elizabeth was reportedly examined prior to France's entertaining the possibility of a marriage with the Duc d'Anjou. Louis XVI's inability to have an erection because of a tight foreskin was a matter of wide report in diplomatic circles and the subject of a frank discussion between him and Joseph II of Austria. The 12-year delay of the future Catherine II after her marriage to Grand Duke Peter in becoming pregnant was the matter of much speculation about Peter's physical capabilities.
In pretender lore, much has been made of a claim by a Canadian to have been Alexis, with some of the evidence presented being an undescended testicle that was supposedly common to both Alexis and the claimant. Moreover, this claimant's proponents have brandished the tale that the Canadian Royal Mounted Police who were sent to check out this supposed Alexis were given a show-and-tell of his testicles to drive the claim home.
So we've heard something of Alexis' genitalia before. Now we have the opportunity to examine them photographically. What's the big deal? Why bother to post a picture of him naked otherwise? We already knew that he went swimming. We already knew that he had bruises from hemophilia attacks. We already knew how tall he was. We already knew that Derevenko was his constant companion in all activities. The only new information in this photo is the appearance of his genitalia.
Lighten up, everybody.