The assertion that a child doesn't feel his flesh being crushed and cut is simply a deception by the medical industry to deceive parents to consent to the procedure.
This may have had some utility a hundred years ago when they sincerely thought there were some benefits to be gained from circumcision but those days are long gone. At that time, there weren't any safe methods to relieve the pain. Many procedures were done without any pain relief even to adults. It made some sense that if there were all of these amazing benefits, to do it to newborns because when an adult considered the pain and the fact that he had no problems *yet* with his foreskin, he was very unlikely to consent to the pain to have it done later. However, that changed long, long ago. Yet, the medical profession found the profits and also found that administering the anesthesia cut into those profits because it took longer. They simply couldn't do as many or sleep in as long in the mornings if they had to take the extra time for the anesthesia.
If doctors told parents that cutting off the foreskin was just as painful or more painful as cutting off a piece of skin the size of the child's hand anywhere else on the body, the vast majority of parents would decline the procedure. They would clearly relate to the quantity of pain and would consider if they would want to endure that level of pain themselves.
It makes absolutely no sense that this one part of the human body would be immune from pain any more than any other part of the body would be immune from pain. All areas of the body are exquisitely sensitive to pain. This is a defense mechanism. Pain tells us that we are causing injury to our bodies and that we need to stop doing what ever it is that we are doing for our own self preservation. Even a newborn will withdraw from a painful sensation. That reaction is there from before birth.
I saw a TV show once about a child who did not have these pain responses. Because of this, the child repeatedly injured itself. It would touch the same hot stove or heater over and over again. It would chew it's fingernails to the point of being bloody and the fingertips were missing to one degree or another. This is what would happen if a child didn't have feelings in the foreskin.
Frank