As far as someone getting amped up by a kick to the groin....... hmmmm.... He must have nuts of steel!
No, just good focus. Others have already related stories of serious damage done, but no visible stoppage of the violence occurred.
One of my previous instructors spent some time in jail (wrongly, in my opinion). He met guys there who LIKE for you to hurt them. They simply shut down once that happens, they stop feeling pain, and go ballistic. Once that is triggered, you must PHYSICALLY DISABLE them to get them to stop fighting (knockout/choke to unconsciousness/break limbs, neck/kill). They will not quit otherwise. It is a truely frightening level of violence.
Stuff happens in fights. Very few (if any) people can actually target specific points in specific places in specifiic orders to achieve a specific goal while someone is trying to take their head. Arts like aikido and Daito ryu do make use of kyusho, but it's kind of built into the system in multiple levels of defense. Evade, block, strike, grapple (and if possible, grab or cut where kyusho are LIKELY to be). But the kyusho are simply an additional factor that MAY prove usefull. You don't rely on them to win the day.
I have a great deal of trouble with systems that RELY on kyusho to save the day. Just look at skilled boxers...even in the fight mentioned above, how many shots did it take to get the opponant in a weak enough state for the liver shot to work? I'm betting it wasn't a first round knockout. Probably more like fifth round, after a significant amount of body shots.