I don’t have a problem with him saying that he didn’t like Han shooting first or that it went against his principles. However, Lucas should realize that that is within Han Solo’s character. It’s like he’s afraid people think that creating a character such as Han is an endorsement of that character.
Maybe some characters would not have shot first because they thought it to be immoral or against principle. Nausicaa (from Studio Ghibli’s Nausicaa of the Valley of the Wind) is one such character who comes to mind. Or maybe even Obi-Wan or Luke Skywalker. But Han Solo never was or pretended to have any sort of Jedi code or morals.
Maybe Lucas didn’t realize how popular Han Solo would become as a character and later came to realize that people thought of him as a role model, which he never intended or wanted. So he felt the need to whitewash his actions against Greedo. If that is indeed the case, it’s not acceptable because it’s revisionism and lacking in confidence to let your creation stand on it’s own, accepting how the fans react to it. But that’s just a theory.

The character Archie Bunker from All in the Family was well, I haven’t actually seen that show so let’s just say Eric Cartman (South Park) was inspired by him. Apparently, Archie Bunker was supposed to be an example of what not to be but a lot of people actually ending up liking his character for real.
Should the creator(s) of All in the Family change Archie Bunker’s dialog to be more politically correct so people don’t have to feel some of the show’s viewers really like a “bad guy” who was supposed to be an anti-role model?