That one seems to go most in depth, and it comes straight form the CDC. Although the rates vary from one STD to the next, the general consensus is that you're twice as likely to contract any STI with foreskin than you are to contract it without foreskin. Other references that vouch that circumcision actually reduces the risk include:

http://www.webmd.com/men/news/20090325/circumcision-cuts-stds

http://www.cosmopolitan.com/sex-love/news/a12466/circumcision-std-risk/

http://healthland.time.com/2013/04/17/why-circumcision-lowers-risk-of-hiv/

Believe it or not, but an uncircumcised guy as the top of the sexual relation is statistically 200% more likely to contract an STD through the pocket under the foreskin than that of a circumcised guy.

That's quite a remarkable figure for STD susceptibility - Could you point to the source for it?  I think it bears investigating more closely.

As for the foreskin being a germ trap, assuming a fully retractable foreskin, washing takes less time than it generally takes to wash balls.  No special thoroughness is needed.  Of course if the foreskin is tight, that's it's own problem as mentioned in my previous post and it would be wise to see a decent doctor about it. The reason for not using soap is that there's a little ecosystem of protective bacteria in there which are benign to us, but actively fight off other bacteria. Using soap can knock these out and leave a guy a bit susceptible to some infections.

After having said that, I'm bad at washing with just water and usually clean in the shower with whatever I'm using on the rest of my body.  In my 52 years, I've never had any problems whatever with my cock.  More than that, I don't think I've ever known anyone I know to have had a problem beyond a standard STD, and with most people I know, we talk openly about such things.

First up on the list would be the risk of contracting an STD. Believe it or not, but an uncircumcised guy as the top of the sexual relation is statistically 200% more likely to contract an STD through the pocket under the foreskin than that of a circumcised guy. This is largely due to the fact that the foreskin creates a trap (or pocket) for lack of a better term where bacteria and other such foreign substances can get trapped, particularly if you do not clean under the foreskin. By this same token, speaking as a guy who has not had the little snip snip, I can attest that if you are not very careful to clean out under the foreskin very well on a regular basis, you'll find yourself at an increased risk and frequency of infections such as strep throat bacteria or yeast infections under the foreskin, which can become rather painful.

On the flip side of that, although the risk of running around with a germ trap is much higher with an uncircumcised penis, there are also drawbacks to getting the little snip snip. One of the biggest downsides that I know of to having the foreskin removed is that a number of people that I know who have had it done later on in life report that the sensitivity in the head of their penis is either non-existent or otherwise severely reduced by comparison after having the foreskin removed. The other most common down side that I have heard of is in cases where the doctor, moyle, etc that is doing the circumcision doesn't do it correctly, thus taking off a little too much skin. In this type of situation, getting an erection can actually be painful as the remainder of the skin gets stretched out much more than it otherwise should, which can cause painful sensations if the procedure is not done correctly. Sadly, it is my understanding that this down side is rather common.

In the US, it's a routine procedure despite the US surgeon general determining that it's unnecessary and results in a number of infant mortalities each year.  The excuse of "I'm circumcised so I can't teach him how to keep it clean" is one i've heard. How hard is it to say the words "Wash it".  Uncut dicks don't come with 300 page manuals; you just need to wash it (ideally without soap) just like you wash anything else.

Some religions practice circumcision as part of their belief system.  A religion that says you have to cut pieces off babies is at best suspect! it's the 21st century; put your brains in gear and rub a couple of brain cells together and see what wonderful things happen.

Cultures that influence you to circumcise - same as above.  Brain in gear and see if you can develop a bit.

All of the above applies even more strongly to female genital mutilation, where the effects are often debilitating and devastating. i don't know of any religion that demands it, but I'm not putting money on there not being one.  I would put money on some advocates trying to justify it in religious terms.

Doctors - recommend surgery as a last resort.  A friend has a Son of 15 suffering from Phimosis https://en.wikipedia.org/wiki/Phimosis. His doctor took one look and recommended circumcision without exploring any other treatment option. A simple web search and some patient stretching and the kid's happier and well on the way to solving his problem.  Doctors should explore the alternatives before advocating cutting off pieces of their patients.  Sometimes it's necessary - no argument there - but it should be regarded as a last resort.

Having said all that, you probably have the notion that I'm against circumcised cocks.  Not at all.  I'm against circumcision for no good reason.  I a guy wants to be cut or someone has a medical condition that's the best treatment option, fine.

As to playing with cut cocks, I do prefer uncut because of the texture, the taste, the sensitivity, but I'd never turn a guy down because he was cut or express disappointment.  I've had a number of guys apologise for their lack of foreskin because they feel incomplete; just one more reason not to cut a piece off someone before they're able to make their own choice. I've pointed many guys toward http://norm.org for free information on easy non-surgical ways to restore a foreskin, or at least go a long way towards doing so.

The US has the highest rate of circumcision in the modern world, yet it has one of the lowest rates of healthy penises.

I think a lot of this is due to the prudishness of American society, especially in post modern feminist americKa.  We can have all manner of dirty vagina ads on tv, but you can't talk about penis issues.  Tits and squirrels are fine on tv and movies, but the world would end if there's even a hint of penis.

Hygiene is the most important factor in keeping an uncut penis healthy.  This is why studies done in 3rd world shitholes show that circumcision is good.  The same studies done in the modern world show no benefit to circumcision.