At the time, Christopher, I expressed the idea that Ellison's ire was a "wag the dog" situation and suggested he was trying to deflect the s/f community's attention from the then-recent Connie Willis groping incident.
I've come to a rather different viewpoint, however. While he may genuinely believe that he, not CBS, owns the Guardian, I now believe that pride is the motivating factor in Ellison's quixotic quest.
In short, David R. George managed to do something that Ellison himself could not -- he wrote a novel. (Well, in the case of Crucible, we're talking three novels.)
Ellison has never been a long-form fiction writer. Never. Yes, there's Spider Kiss, from forty-some years ago, but it's not science fiction (it's actually a rock-n-roll novel) and I think it's properly novella length. Ellison has always listed forthcoming novels in his bibliography, often as not expansions of something else he's written, yet they never surface.
So, here with Crucible, we have an author taking something he created, who expanded it into an entire trilogy of novels.
Ellison couldn't have done that. I suspect Ellison knows that. And I believe that's what has raised his ire. The existence of Crucible reminds him daily of his own limitations.