To be fair, the brain has the skull protecting it, while the testicles are quite vulnerable. Additionally, because hockey is played pretty much at ground level instead of head height, the testicles are in more danger of being slashed by a hockey stick (I got hit in a pickup street game without a cup, and while it's not exactly the most painful place to be cut, it's still not very pleasant when you go to the bathroom and realize you're still bleeding) or smashed by a flying puck or sliced by ice skates than the head is. Also, your head has a much wider range of motion if you need to dodge than your testicles do.
Wow. Scroll down far enough, and he actually makes fun of someone for acting like they're 9. Amazing.