Would Hardee automatically take command, or would there be a dispute over who the interim commander is? If there is, then the rebels aren't going to be able to easily ready any effective response if there's any disagreement whatsoever between corps commanders (which there almost certainly will be) and no overall commander who can give the final word.
Also, even if the mutiny helps morale in the long term, it will destroy discipline--many commanders, especially field officers, might not want to risk leading their men into situations that the men view as unfavorable, and the men have no real reason to do so at all unless and until discipline is restored, which will be hard to do while also fighting a campaign against a determined enemy. The rebels probably wouldn't melt away, but it's hard to imagine them having the discipline and confidence to properly respond to any assault.
Maybe I'm wrong, there might be reason to believe discipline would spontaneously restore with the removal of the unpopular commander. However, there are very few examples in history of any frontline mutiny ever resolving the issue so neatly.