I'll use a lightly less (maybe) incendiary topic than Woody Allen - Han shoots first.
Lucas clearly was establishing that the SW universe was a bit lawless like the "old west", that Han was a potential wild card and a contrast to the more naive/idealistic Luke, and so when he leaves with his reward on Yavin IV Lucas has created some (minimal) doubt that he really is only in it for himself. So it works to establish the world and the character and his arc in the film.
But later, Lucas became uncomfortable that one of his 3 main heroes, who kids were idolizing, had killed Greedo and was pretty callous about it like it was no big deal. Even though Greedo was somewhat menacing and threatening, Han nevertheless may or may not have been in a "feared for his life" scenario where it was self defense. So he decided he was more comfortable if Greedo more overtly was a threat, so Han was justified. (Of course many geeks and nerds have debated this endlessly) From an artist standpoint, Lucas deciding he didn't want one of his heroes to possibly promote a "shoot first" message I thought was his choice and came from a good place - he was taking some ownership of the perception of the character and the potential impact on young viewers.
Now, I didn't think it was a needed change but I am never going to complain about making a hero more noble is a bad thing.
But one thing I find interesting is how that scene might change under different conditions -
Greedo is some creature we have never seen before and is like killing a "monster" in sci-fi terms, so it is mostly fantasy.
What if the bounty hunter was another human male that was Han's age, and Han shot him first? Does it play different that it is human and not an alien we have no connection to?
What if the bounty hunter was an 18 year-old kid like Luke, who is nervous and sacred and says he doesn't want to bring Han in but his family needs the money? Does it play different if Han shoots him first?
Art always has context brought in by the artist, especially narrative fiction, and I think the person creating the art needs to think about that.
Another great example is Clockwork Orange, and the reaction to it, and Kubrick possibly pulling the film due to either threats against his family or his own concern about some people copying the Droogs despite how he depicted them. Absolutely fascinating film, especially compared to the book, which in the UK version had a chapter that tonally changes the story compared to the US version which does not.
This is great interview from the time where Kubrick talks about some of the same issues as to artistic intent and responsibility -
http://www.visual-memory.co.uk/amk/doc/0070.html