First off, let me make this clear. I know what it's like to get the crap beat out of me by more than one person. In particular, one time I was stomped, and along with the obligatory black eye, I had sneaker marks all over me. It was kind of interesting, you could see the treads of the shoes on my face and shoulders. I've been hit by a 2X4, I've been sucker punched, etc... but this was distinctly different. The blows were kind of interesting, muffled somehow, it stood in contrast to other situations because I'd had blows rain down on me before, but not like that. I didn't really make out what was being said, I wasn't even sure exactly who had kicked me and who hadn't.
It didn't cause any perceptible change in my behavior, other than my brother didn't want me playing basketball for a while (I finally snuck away to play a few months later). So, while I can relate to a severe beating, I can't relate fully to the psychological fallout (although I did feel betrayed).
Having said that, I've also been on the other side a bit. When I was a teenager I started hanging out with one of my older brother's friends, a complete lunatic, and he was perpetually doing stupid and dangerous things. My hanging out with him was a part of my destructive behavior, which included almost being shot by him when he was drunk/pill popping/eating shrooms. He once went around scouting houses on a Sunday morning out in the country, talking about breaking into one (which could have easily ended with a shotgun blast to his gut, or mine should I have joined him). I don't know what all he did when I wasn't around, he talked about lots of stuff. The crimes he did when I was around, while some would be felonies, typically involved some sort of substance, speeding, that sort of thing. Almost shooting me aside, the most harmful thing I saw him do, was steal a hubcap.
I'm not defending my actions, nor am I defending his. But! This is important, I'm not someone who ever made a habit of harming others. I didn't try to hurt others, I don't believe I've ever done serious harm to another, I don't even like to go hunting, or to kill a bug. If I had continued to hang out with him, there's no telling what incredibly stupid idea he might have gotten into his head. What kind of harm he might have done to someone else, be it overtly maliciousness or just recklessness. Would that be my fault? Sure, partly, but he's responsible for his actions in the same way I'm responsible for mine.
I never bought the idea of charging the guy sitting in the car with murder. I never really got the notion that simply being present makes you as guilty as the other parties. That's illogical. Sure, you shouldn't be there, sure, you should have stopped it, but have you ever tried to stop a friend from doing something stupid? Have you ever refused when you're out numbered? I had someone threaten to kill me because of a refusal. At another time, over a disagreement (I was accused of being a member of the NAACP for my position on the matter), they threatened to drop me off in the middle of nowhere. This isn't to defend the actions or the consequences, but I do not believe it's fair or rational to treat everyone present as equal participants. That's not how things happen, and it's extremely rare that all actually equally share blame.
So, in terms of the Pettway incident, I haven't seen anything to indicate he was actually guilty of participating. I seriously doubt Alabama would have invited him back if they believed that to be the case. Was he there? Yeah, but from what I've followed of the case, he was treated different from the two attackers and I have no reason to believe this was for any other reason than he conducted himself differently. May be I'm wrong, I don't know, if someone can produce evidence that Pettway was an attacker then I'd argue he might have gotten off too lightly. But, from what I know right now, his crime was that of going along with what other people were doing, which is wrong, which is serious yes, but does not involve an actual act of aggression against another.
In short, I trust Saban on this. He let Pettway back for a reason, and if Pettway's role was as a bystander, than I can certainly understand that. Can anyone refute that? It appears to me that a decent kid might have made a mistake of hanging out with the wrong people. If that is the case, I can certainly see the grounds for forgiveness.