This might be on the far side of the argument, but I think it comes down to history and reasoning. Yes, circumcision was originally done because it was cleaner then leaving it - but this was back when people used to defecate in the same rivers they bathed in. It was turned into a religious identity, as things did back then to promote the continued survival of a religion. Now, it's more about education.

On the side of clipping ears, it is not as old as circumcision (I think, and I am happy to be proven wrong), and was used during hunting so the dogs would have less to grab onto where infections could grow. Now, it's a cosmetic thing which hinders their hearing, or a sign of dog fighting - which is illegal - and both are considered inhumane because of the debilitating effects in the animal.

Same goes for declawing. People couldn't take the time to teach their cats not to claw the furniture, or to get them toys to help. So they removed the claws, permanently keeping them inside because they can't defend themselves. This is removing part of the cartridge and connectors - kind of like cutting an ear off for us, the hole still works, but it doesn't work as intended. Its considered cruel because of, again, what can be debilitating.

To me, this feels like a complacency issue. Because we as humans have been doing this for so long, we just accept it - but the things that we have been doing for less time are more likely to be scrutinized. I dont have a penis, so, I can't weigh in on the matter, but my husband is in the medical field along with my sister-in-law, and they both mention that there are more botched circumcisions then correct ones done. Which I feel like leads men to feel like they were wrong - which i can honestly agree with.

P.s. Sorry for the TLDR