This is one thing that I don't think many people have considered. One of, if not the biggest complaint from your supporters has been around the attitude and application of a lot of your players. How does a manager that's already struggled to deal with this issue, turn this around after having his position undermined over the past month or so? Getting multimillionaires with huge egos to fall in line is hard enough at the best of times but when they believe the manager doesn't really have the support from above, that can only become a bigger challenge.
That said, it is a bit of a no win situation for Utd in that regards because sacking the manager will only reinforce the belief that some players will have that they're above the manager too. I'd suggest a new manager coming in, at least in the short to medium term would have greater authority than ETH has now though.