Your head would have exploded if you lived in Victorian England, when parents' pictures of children to send to friends were often naked (and in some form of frolic!), because it was viewed as childish innocence. You seem a little pedophilia-centric in your worldview.
Were the parents naked with them in the photos? Also, I have no idea in which country the photo in the OP was taken, but if it was in the US, and if it was my neighbor who showed me the photo, I'd think some weird shit was going on in that house, as would most of the people I associate with outside of this board.
The day that you are regarded as a moral authority on this board is probably the day I stop posting here.
I'm going to guess you don't have kids. I'll also guess that you've repeatedly looked at the photo. My third guess is that you don't know what "puritanical" means.
That is a weird picture that I can't imagine most people would ever want to receive from friends or family. But illegal? Or immoral? Or even "sick"? I don't think so. Ed O.
I showed the picture to my wife. She was speechless for a good 30 seconds. I'll guess we'll just be the fuddy-duddies with kids. You single guys seem to be embracing it, considering the defending of the photo I'm seeing. IMO, if you don't find anything wrong with that photo, you probably should not be a parent.