I don't even see the point of the argument. It was clear Greedo was to kill him. It doesn't matter who shot first it was self defence either way, and even if Han shot first it was no cold blooded kill, it was a him or me situation.
Whats the big deal? It makes no difference what so ever.
It's a black and white morality thing.
The hero is never supposed to swing/shoot first.
As Lucas has aged, his morality seems to have shifted to a very black and white vision, and he's changed his work to reflect this.
Compare the amount of people Indiana Jones kills in the first several movies to how many he kills in Kingdom of the Crystal Skull.
For whatever twisted reason, Lucas seems to now believes heroes should never, ever kill.