When I was in med school assisting in circumcisions (didn't want to, had to) the doctor said that the baby screaming was not proof that he felt pain, and demonstrated it by poking the baby and showing that he cried as a response to that. Absolutely nonsensical for a supposedly intelligent person to say. The cry was vastly different from the circ and a poke. It was an excuse not to use local anesthesia or justify the whole process I guess.
The funny part is that that when I was on OBGYN at a different hospital, and when I was at my home hospital on peds, the pediatricians did circumcisions. So I got twice as many circumcisions as my classmates. Some of them could have theoretically attended zero if their schedule was flipped and they were on peds at the OBGYN circumcising hospital and on OBGYN at the peds circumcising hospital. I can't understand why someone would claim someone else doesn't feel pain. I wish we had a machine that could make someone feel for a second what you feel so that it stops being minimized or disbelieved.