Circumcision is suspected by many to actually lead to desensitization the glans (head of the penis), as this part of the body was not designed to be constantly rubbing against clothing. In theory, the incessant stimulation of the members of circumsized males will reduce the sensitivity—thus making sexual activities less pleasurable. Unfortunately, I haven't heard of an actual study of this phenomenon.

Infancy is exactly when one does not want to be subjected to the sort of painful trauma experienced during circumcision. Having parts of one's genitals chopped off is traumatic at any age.

Circumcision is not necessary for cleanliness. The uncircumcized penis can be easily kept clean: a simple 15-second rinsing every time one showers is an effective and simple method of ensuring sanitation and well-being.

While it is certainly nowhere near as severe as female genital mutilation, it is still no simple medical procedure. It's a bizarre, barbaric, and completely unnecessary practice.