Lets not slice around the head of the issue. Circumcision is a somewhat terrifying ritual practiced for religious, cultural, and cosmetic purposes.
Circumcision is the removal of the foreskin from the penis, preferably by a doctor. It is oftentimes done for tradition, paternal resemblance, and religious reasons, although it's a statistical fact that someone out there has done it on a drunken dare.
Don't let this doctor do it.
The trend of circumcision is dying out in the United States due to a growing mindset that maybe a baby shouldn't experience sheer agony as one of its first sensations. The counter argument is that they don't remember the pain, and having it done when they're older would be much more painful, memorable, and less enjoyable. It's also sometimes necessary for medical purposes.
The Judaic and Islamic faiths demand circumcision. It is the sign of the Covenant between man and God. Some people have questioned why God couldn't have made us sign a contract or pull out an eyelash instead, but they don't understand. If you cut off part of your dick, you're probably 100% loyal.
There's just one more thing you have to do before you can join the guild.
It's actually so important that if a Jewish man dies without being circumcised, people will take his rigor-mortis stricken member in their hand and circumcise him right there. We suspect that at least one person has secretly done this for bad skin treatment (6 Valuable (And Disgusting) Ways They're Reusing Human Waste)
There has been no definitive proof that circumcision decreases the pleasure begotten from sex. We're guessing it probably has something to do with the lack of volunteers for such a survey. Although some people claim that it has caused them great emotional distress over their lifetime, there is a general consensus that if your circumcision was the most scarring part of your childhood, you probably had a better childhood than most people, and should stop complaining.