ya..shot to the nuts isn't as easy to do as one would think..as pointed out..natural defenses lol..aim has to be just right.. foot stomp only works if standing lol...
eyes, nose, ears, struck using palm of hand and NOT fist, and gouged at with fingers works nicely if a guy has attacked you and is on top of you.. hard to "fight off" a quick shot in the nose or a nasty eye poke and rip...
in the end.. i encourage anyone to take self defense classes in what ever martial arts interest them.. there is no right "art" just whatever works when you really need it and gets you to safety..