I think Radley Balko, in his defense of the Mehserle verdict, has it right:

There's also the appearance of a double standard. Mehserle's defense is that he made a mistake. In the heat of the moment, Mehserle inadvertently reached for the wrong weapon. But Mehserle had training. He had other cops there backing him up. If we're going to be sympathetic to him, we should also show some sympathy and understanding for people like Cory Maye and Ryan Frederick, both of whom were tried for murder for killing police officers who broke into their homes at night.

Precisely. I can understand juries giving Mehserle the benefit of the doubt. But the fact is that that benefit of the doubt doesn't extend to everyone else. Read up on Cory Maye. I'm not looking for a harsher sentence for Mehserle. I'm looking for the rather compassionate judgment he received in California to be extended to non-cops.