That doesn't really cover any of the points I was making outside of one intentional twisting of a sentence without the context. He used the dark side to maim Vader. He was doing it in anger and with dark intent over Vader's taunts about Leia. That's canon. And not what Yoda and Obi-Wan had in mind as the motivation to destroy Vader. They wanted him to destroy the threat but not turn to the dark side and just replace Vader in the process. And that was close to happening, but Luke overcame. And that is the entire crux of the argument. It is established within the character beforehand that he can consider dark intent even momentarily, and thus the prerequisite you yourself set is matched. This was established within the character over 35 years ago.
For the record I'm not arguing Luke was right or justified in what he did. It wasn't, it was a mistake, and it was within previous characterization (and indeed the characterization of any Jedi) to imagine making an unfortunate mistake. It wasn't wildly out of character. I respect anyone with the opinion that such a creative choice shouldn't have been made in the first place, so be it if that's the way one feels, I can understand that. But its just not unimaginably out of character when put to scrutiny to not only his character but most importantly above all the rules and the risks of the religion he practices.