Years ago my daughter-in-law posted an adorable picture on her blog of two young (under 3) grandchildren in the big tub taking a bubble bath. Unfortunately one of the kid’s lower area was a bit exposed - I told her to take that picture down fast, or some sick person would report it and her for child porn or something equally awful.
I may be have been overreacting, but in this day and age, I don’t think so.
The problem is not that images of that type are “dirty” to any normal person. It’s that there are abnormal people out there who find them arousing.