Wow.
I'm not saying I want any rules changes at all. That was (IMO) Bush's fault entirely, plain and simple. It seems these guys forget that when you turn the car, you scrub off speed. It's similar to what happened either last year or the one before where Vickers took out the front runners and won. All it took was for Johnson (the one Vickers was pushing) turned out of line to pass Jr. Once Vickers found out what was going on, he turned down to help Johnson, but since he had already scrubbed so much speed, Vickers ended up turning him into Jr., giving Vickers an easy as hell victory.
Usually in a situation like this though, once it's repeated a few times, NASCAR comes in and rearanges everything in the name of "safety."
With years of simulated experiance like this, I have to say, I would have done the same thing as Bush, then realized after viewing replays that I might have still gotten the win if I wouldn't have blocked a second time.
As for it being the spotter's fault, I don't think that's fair. It happened so fast that by the time Bush would fairly be expected to react to his spotter saying "Car high" or anything of the sort, would be watching all the cars infront of him as he was spinning... Also, when you're as excited as they must have been, it takes even more time for someone to register something like that.