The best link I know for circumcision I highly recommend the Penn and Teller page.
Of course an adult who has it done for medical reasons isn't going to find that his sex life is worse, he's most likely going to find it improved! Men who have it done as adults for cosmetic reasons don't agree, they do find it makes their sex life worse.
I'm shocked that anyone uses a plastibell for religious circ, it's far from a traditional circ which is removing a slither of skin (not that I'm justifying it) plastibell is straight out of the USA and is full amputation of a healthy working organ. Have a look at any painting of a naked baby Jesus and to our eyes He looks intact that's because compared to that He is, He would have had a small amount removed to fulfill the covenant. If full amputation was done in Abraham's day then most boys would have died. RIC is the leading cause of infant death in the USA.
I broke my nail recently, right across the middle, ripped the nail from the nail bed and it is the worst pain I have ever experienced! Amputation of foreskin of boys does pretty much the same thing, rip away skin that is fused to skin.
There is a law that can be used against RIC (in both the UK and USA) so anyone who does it needs to consider that.
A lot of Jews, Muslims and Christians (in the USA "religious reasons" is being stated by Christians too) are now speaking out against it, all using scriptures to back it up (Christianity is the easy one it says over again not to do it as it does about eating meat "do not call anything I have made unclean").
My partner was done for medical reasons that I won't go into here. He's not my first partner so I have got comparison. Sex with him is brilliant, however I do notice the difference. He didn't have a full amputation so has some movement but he is dry and keratinised which is uncomfortable as I need to provide more moisture than if he was whole so sometimes it hurts. The head of the penis has sharper edges so it rubs against the walls. Imagine having sex with a plastic penis with no lubrication and that's pretty much what you have. My partner is the biggest British intactivist I know. His son was done for the same reason (inherited from him) and he was heartbroken for him.
I am a breastfeeding advocate, a Doula, a peer supporter but this is a totally different issue. RIC kills more children than anything else in the USA, even more than formula does. It's irreversible and there are so many more negatives. I would rather feed my child completely on formula than mutilate them.
The reason that it continues is the same reason hazing continues, only this is different. You have to admit your parents allowed something bad to happen to you.
RIC doesn't prevent HIV, the study had to be abandoned early because so many of the participants had caught the virus and it was an incredibly flawed study anyway. There are no medical benefits accepted by any medical body in the world, in fact the opposite.
Oh and if you look into the difference between clean and unclean animals you find that it's the amount of stomachs they have. The more they have the more their food is processed.