Some people just freak out at the thought of this procedure. I have witnessed several (of my own sons and grandsons) and the entire operation takes a few seconds. There is NO WAY a person could "get off" sexually by doing this, not to mention that there is a crowd of people present during the ceremony.
i doubt if most of the people performing the ritual would become sexually aroused. however, if a pedophile happened to be doing the ritual, his response would be arousal, and all the people there might only add to it.
there are people who become aroused by all sorts of things that would not be arousing to most people. do a search for "paraphilia" and you will be very surprised.