Rabbi says that milah removes something bad while Rav says it is an act that endows an otherwise unattainable good. The thrust of Tyranus Rufus' argument with Rabbi Akiva was that by performing milah we are saying that G-d's workmanship is flawed and we are correcting it. This perverted view of our mitzvot in general and of milah in particular persisted for a long time. Even Rav Sadiah Gaon had a need to refute the idea that milah is inconsistent with professing G-d's perfection. First of all, the Rambam says that indeed the act of circumcision harms the male but that this harm needs to be done in order to achieve moral perfection.
Circumcision is done to rein in sexual drive.
The other reason to perform milah is that it provides an indelible sign that the person is a member of the community of Avraham Avinu. The Rambam notes that group cohesiveness is enhanced by possessing a symbol o f membership. Milah is as distinctive a sign as one could imagine and by its nature does not invite imitation by other groups. There is one last issue that I would like to discuss. Avraham Avinu was able to derive the whole of the Torah by starting out from his perspective on life.