It's still not clear who started the altercation, just who ended it. If, for example, Zimmerman had grabbed Martin by the arm at the beginning of the confrontation then Martin would have been justified in defending himself. But we'll never know.
And that's where I believe self-defense laws are flawed. I have no problem with self-defense, or even self-defense with deadly force. But I have a problem with self-defense with lethal force when the only other witness is dead. It's a Catch-22. In order to allow justice via self-defense you open up a massive loophole for the gravest of injustices. That bothers me. And you cannot legally force the shooter to offer up evidence or statements that would indict him without running afoul with the Fifth Amendment.
What bothers me further is the Zimmerman had no reasonable expectation to NEED to defend himself. He was in his car, safe, and armed. If Zimmerman had no intention of confronting Martin, he had no need to take the gun from the car with him. Now, legally, of course, nothing stopped Zimmerman from leaving his car or confronting Martin. But Zimmerman failed utterly to do the responsible thing and Martin was killed because of it.
There are many other scenarios where one can act technically legally but tremendously irresponsibly although few have as dire an outcome as self-defense with deadly force. That drives me to the conclusion that responsibility should be a prerequisite for gun ownership, especially if you are going to carry. But the pendulum is swinging the other way, as we seek to reduce the responsibility requirements for gun handling. Putting deadly force in the the hands of people progressively less capable or wise to use it (or more specifically, NOT to use it) is bothersome to me. And I'm fully aware that the 2nd Amendment, as currently interpreted, means that is not going to change in my lifetime.
But do not misunderstand that with self defense laws as they stand now, some innocent people will die so that other innocent people can protect themselves. It is not a cost free equation on either side, and the cost will always be innocent people's lives. It is up to all of us to decide which dead-yet-innocent population we're more comfortable with.