I think there are reasons to be opposed to male circumcision. This is also evidence, although it may not be medical evidence as such. The fact that orgasm takes longer to attain is additional evidence. Intensity is a separate issue which is not necessarily related to sensitivity. IMO, what's bad about it is that men are different to begin with and so are circs.
Some men are much more sexually capable than others.
Some circs are much more drastic than others. Combine a drastic circ with an individual who wasn't that capable to begin with and you may have a seriously hanidcaped individual. There are all kinds of circs. The fact that the loss isn't often this damaging doesn't mean that there is no sexual dysfunction involved. Let's face it, it is mutilation by definition since no disease or trauma is being treated and a statistically healthy and useful body part is being removed.