It does make the case less complicated that he's White and shot three White men. But it comes down to him taking a gun to a riot, and then bad stuff happened. I think they have to punish him for that, else lots of people will do that. And what people think of as "the good guy with a gun" is not necessarily going to win next time.
The basic problem is "Stand Your Ground". All states used to say you had an obligation to retreat, if things got out of hand. Now many states, and many people, think they should just shoot anybody they fear. But there is fear on both sides in any conflict, and these laws just protect the last person standing no matter what he did.
We're flying electric helicopters on Mars yet you can't turn on your clothes dryer in Texas. That's because scientists are in charge of Mars, and Republicans are in charge of Texas.