Does anyone really care? He was easily the worst actor in the JL cast, and that wasn't Whedon's fault. The guy is absolutely joyless and incapable of emoting, even by the standards of an actor expecting to make a Snyder movie. I'd prefer he takes Ezra Miller with him (especially after the stuff about Miller that has came out), but I doubt anyone will miss Fisher.
No, Zach Snyder was the worst director anyone could have hired for the film, or any film outside of that Ayn Rand shit he's trying to make now. That isn't to excuse any potential abuse, but Whedon as a film maker is much more skilled then Snyder in literally every way possible, if he'd been on Justice League from the beginning it would have been at least a decent flick. Snyder never was going to make a good JL film, and now he's going to produce another joyless pile of unheroic, Objectivist inspired crap as a four hour mini series that most people will hate and will definitely not justify its additional budget.