It's not the legal consequences that matter in this example but the financial consequences. In this example, the acquisition apparently had a big stock component. So now his financial interests are aligned with the rest of the company's owners. If his hypothetical rage-blogging were effective, it might hurt the company's value which be a big hit to his finances.

The point of the anecdote is that these deals are designed to align the acquired with the company if there are personal-career-satisfaction/play-along-nicely conflicts.

edit: typos and a recognition that this point was already made well while I was typing.