Of course circumcised men don't think it's mutilation because most of the time, they've never lived with a foreskin. It has a purpose. It's easy to say it's not important if you've never had one to begin with.
I think mutilation is too strong a word, but I do find the practice... bizarre and undesirable.
/shrug
What is the purpose?
What's its evolutionary purpose? Not too sure. Maybe to protect the head of the penis and thus to ensure its sensitivity for sex, which results in more pleasurable sex, which means more babies, and thus the survival of the species. That's my hypothesis.