The biggest problem with ‘self-defense’ is that it says nothing about what has to happen to the other guy. Or, to be blunt, it says nothing about what you have to do to the other guy. And that missing something is probably whatever it is that he wants to do to you.
Think about it this way: do you really think a serial killer is worried that someone will use ‘self-defense’ on him? Is ‘self-defense’ what he does to his victims? Not hardly. If anything, he’s afraid of being stabbed in the neck, or shot in the head–if anything, he’s afraid of what he knows works. And even then, the criminal sociopath doesn’t spend much time worrying about someone doing it to him. He puts his focus where he knows he’ll get the best result–he focuses on doing it to others, first. And that ‘it’ is violence.
In swimming, simply having the idea of ‘not drowning’ isn’t enough. You need to know, mechanically, how to move yourself through the water. Likewise, you don’t survive violence simply by seeking to thwart a negative outcome, to counter what the other guy is trying to do–you survive violence by hurting people. You win by crippling, maiming and killing. You win by using the tools and techniques of the killer against himself. You win by doing what works.
In the end, if you don’t know how to hurt people, put them down and keep them there you don’t know how to survive–and win–in the realm of violence. And you’ll always be one neck-stab behind the guy who does.