I live in a country where most males are circumcised and the only ones I know who've suffered any ill effects, are as a result of malpractice, something which occurs enough in all fields of medicine.
So no, I don't think one is justified in calling it mutilation or barbarism.

There is no logical connection between those two sentences. Putting "So" at the start of the second does seem to seek to imply that there is.

It doesn't hurt if you have it done to you as a child, but it would hurt a great deal if it were done to you as an adult? How convenient. Isn't it possible that it hurts in both cases, but our memories of what happens to us as babies are not normally accessible to us in later life?

The strange thing is how this rather odd cultural idiosyncracy became common practice in the USA in a secular context, whereas in most parts of the world it has been more or less confined to the field of religious ritual.