Of course, for men who are circumcised and so who already lost most of their ability to feel what sex is...
Sorry, pal, but I think you're on the wrong foot here. I happen to be circumcised - my dad was a Baptist and considered it standard procedure - and while I do find the idea of the ritual and especially its religious reasons to be beyond bizar, I personally, gladly, am fine with being circumcised. I've heard there may be medical arguments that are pro-circumsision - couldn't say for sure though and don't really care. It was done when I was freshly born, by a doctor and with anesthesia - which is the *only* acceptable way to to it, btw.! . As a kid I thought of it as a simple anatomic variation, such as color of hair. Now I know better of course.
I could imagine that from constant exposure the tip of the penis of somebody who is circumcised perhaps gets less sensitive over time, not sure about that though. Could also be the regular manual work I do and access to infinite pr0n I have - just like the rest of us. (BTW, fellas, check out the Nobnom challenge).
As for the sex, I can assure you, I *do* know what sex is (gladly) and I've had my fair share of female intimate partners, most of which, thankfully, were awesome up to flat-out stellar, p*rnstyle playmates. And I can also assure you, do hookiepookie in the right mood with the right partner and the right amount of moisture in her vulva and Ooomph in your member way more than anything else determines wether you feel what sex is or not. Likewise, play Closet-Polo with someone who is a turnoff and can't keep the mood for 5 seconds, and you'll never know what sex is, no matter how intact and sophisticated your foreskin may be.
Keep that in mind before you go about telling everybody that circumcised men don't know what sex is - some might take offense in that, as you can see here in this thread already.
My 2 cents.