Except the reality in which the criticism is well-deserved, obviously. That's subjective, of course, and I'm not commenting on whether it applies here, but "zero public outcry allowed, no matter what's happening" is an absurd position. Of course that doesn't mean you shouldn't expect consequences, even up to being fired by the tyrant in question, but that's not the same thing as "unacceptable". Employees aren't slaves.
Again, what she did was akin to printing out the statement and stapling it to a bulletin board - or, mass emailing it to everyone in the company. It was an official internal channel everyone in the company can access...
Imagine one of your reports saying something like this about you during a team meeting, while you're standing there. Not acceptable workplace behavior... and that would be limited to just your team.
Actually, yes, yes it does. There are some things you can't say to any employee of any rank: racist or sexist harassment for example. And commenting on the performance of an employee that doesn't report to you is also generally a no-go. But legitimate, job-related criticism of the CEO, or any other senior management, is entirely acceptable. Why wouldn't it be?