I'll be your friend still. But then, I live up here in Canada.
It's a bad law because of the vagueness in it's writing. Intentions mean nothing in a law that is badly written and flawed to the point that it fails.
First of all, I'd suggest that any law dealing with self defense is going to be vague to some degree, since that is always subjective, and is always to some degree subject to further review by the justice system.
Secondly, not living here, I can see you don't know the history of these laws. The fact is, self defense laws in the US are a hodgepodge of differing tests and assumptions. But for quite a long time, they entirely favored the criminal. We had cases of homeowners being sent to prison for shooting armed intruders in the middle of the night into their homes. Cases of carjacking victims being sent to prison for shooting their jackers, who were also armed.
These cases had in common laws favoring the criminal, (self defense was either not allowed, or allowed only under very specific conditions with very specific responses), and prosecutors hoping to make a name for themselves by showing that they wouldn't tolerate "this sort of thing", though evidently they had no problem with the original criminal's intended crime.
We also of course had cases of civil law where a home burglar would sue the homeowner because he tripped over something in the person's home while trying to rob it. Successfully sued, I might add.
The final point I have is that everyone speculating one way or another on the law does so it seems without having actually read the thing, relying on someone else saying it was bad or good. Even if you do read the law, determining it's relative effects can be tricky.
For example, the main arguments against this law seem to be that more people have been shot under it. Well duh, if people know they can defend themselves, they are. Then the argument branches out by saying that some of those people shot must have been shot wrongly---without citing anything at all. Just their own opinion presented as fact. Here is a solid fact---overall violent crime has dropped since the introduction of that law. Whether there is a correlation or not is something I can't say.
It's the same thing we saw every time a jurisdiction introduced a "Shall issue" CCW, (concealed carry law). You had one side proclaiming that as soon as the law took effect, it would be the "Wild West", with shootouts everywhere, and blood in the streets. These people included many police chiefs BTW. You know what? It never happened, not in a single place that they were introduced. You know what did? Violent crime stats plummeted.
So it seems that based on available evidence, empowering ordinary people to defend themselves isn't necessarily a bad thing, except for criminals, police who lose power, and criminal advocates. Was Martin a bad shooting? Don't know, it doesn't seem so right now, but an investigation will help determine that. If it isn't undermined by the sort of intimidation tactics we see being brought to bear now.