For many years it was said that there is no medical reason to do it. There is a very slightly higher incidence of penile cancer in uncircumcised males but that was about it.
Recent research shows that there is a higher incidence of HIV in uncircumcised males probably because the virus can remain longer under the foreskin than on the surface of a circumcised penis.
I think the most complelling argument for it (or against it for that matter) is social. Boys grow up with enough consternation about their penises the way it is. If he sees that it's different from Dad's, his brother's, the other kids at school, etc., it can cause some psychologiacl problems. Because here in the US the rate is now about 50% it's becoming less of a problem. Mutilation? I think that's a rather harsh word. Unnecessary might be better.
I'm against it...
Dutch documentary with English subtitles:
"Mother, why was I circumcised?"
This personal documentary follows journalist/filmmaker....
http://video.google.com/videoplay?docid=-7272603373993370309