I don't think Mark's answers are necessarily unfair either, he's running a business after all. He does have a fiduciary responsibility to shareholders, even if that means making difficult staffing decisions (still true even if they were his fault to begin with by over-hiring). Ultimately you agree to participate in this framework by accepting a job at a public company.
But there is a point after which it becomes distasteful. It gives me the same sort of feeling as those stories about companies pulling offers right before the start date, after an employee has quit their previous job. Legal? Yes. Justifiable? No doubt. Morally? It's grey. And it leaves a sour taste. On an individual level, it's the kind of thing that is punished in the long run, through reputational damage. In an ideal world I would like to see companies face something similar.