There are tehcniques that the Shaolin monks are taught that allow them to be able to withstand such strikes. I have also seen demonstrations of someone using one of the japanese styles withstanding groin strikes as well as strikes to other vital areas.
Also statistically there are about 1 in 20 people that have a natural immunity to such strikes. Personally, I wouldn't want to chance testing weather I was one of the people in that category during an actual fight.
As I understand the technique of resisting those strikes one method is to use muscular contraction to draw the testicles up into the body into the cavity from which they originally descended. This, as I understand it, takes several years to learn and requires a considerable deal of focus and concentration in the heat of combat.
The other method involves learning how to channel CHI (KI, QI) to specific areas of the body at will to strengthen that area to be able to resist it.
Anyone that says they can teach either of these methods, but won't demonstrate their ability to do so, is full of something.
I've been in the martial arts for 33 years, and an instructor for 27 and I wouldn't even risk taking a shot there...
Even if you can learn to ignore the pain and believe me ANY pain can learn to be tolerated, the physical damage is another matter. I knew soneone that faught n a trounament wiht 2 broken ribs. didn't take anything for the pain, just ignored it. He died from a punctured lung.
IF you want to learn to do this let me know and I will find the name of the person that teaches it, it's in my files somewhere....or you can go to shaolin and spend years studying...otherwise...just rely on defensive techniques...