I think the NAACP is filling in for Sharpton on this one. Sharpton may show up at the appeal stage.
It was actually only one bat. It seems improbable that John and Aaron White would have left the security of the house to go out to confront these teen drunks unless they were pretty sure the kids had no guns. If you think the guys outside have guns you don't step out to shoot it out with them point blank range; if it looks like it's going to come down to shooting you stay inside and shoot through the windows - or maybe you do something radical, like call the cops! In any case, It's a middle class area and it's understood that kids don't pack guns there. The Whites were pretty sure they had overwhelming force going for them before they stepped outside.
Sure, John White was entitled, even if not in law, to do something. He could have aimed for a leg, or he could have shot up their cars - but to walk up to the kid and shoot him in the face! Very disproportionate.
If John White is sympathetic it's because he was trying to better himself and provide a safer environment for his family - an iconic American ambition - but his background ( ghetto street justice ) got the better of him. It's a sad situation, but John White has to atone somehow; that 17 year old kid will be still be dead long after John White gets out of jail.