My DH very much wanted to have our DS circ'd at first. After I destroyed his argument that daddies and sones should look alike (DH has 1 testicle... so... stupid argument) he turned towards the cleanliness factor and sexual functioning. His best friend is intact, and he's had issues. Hence my DH thought that the foreskin caused it all. It got a little heated at times...
Basically, the clean-factor is a non-issue. With DH's friend, obsessive over-cleaning lies at the root of the problems. Just as a woman will get all nasty if she uses harsh, scented soaps in sensitive areas all the time, so will a man. Treat boy bits with the same gentle care as girl bits and things should be fine.
And regarding "oversensitivity"... I had to remind him that plenty of circ'd guys also have problems with stamina... and on the flip side, lack of sensitivity can be a HUGE pain, literally, as we know from experience. Marathon sessions are all well and good when I was 22, but.... yeah.
Then I had him read some calm rational literature about circing and he came around.
The history of why circing became the norm in the US was particualrly helpful.
I think it's a terrible thing to do, but I don;t think many people who are initially pro-circ respond well to "mutilation!" Read up, get educated, and then ask why would you want to do it? Once you learn about it, it doesn't make much sense.
Mom to two intact boys, born at home. DS1 11/07, DS2 9/10