He gloated like this with you in the room? I'm only a little shocked... not that he'd gloat, but that he wouldn't think about the effect this might have on the morale of his new hires.
Even when you rephrase it charitably, it still sounds like the acquirer's CEO is talking trash about someone these employees have followed for years.
At best, it's a "you guys are great, but your ex-boss is a terrible negotiator and didn't know what you were worth." There's no reason to say that aloud.
It wasn't that the founder was a bad negotiator, he was just outsmarted. The agreed share price was tied to a metric that the acquirer understood much better than the founder.
Seems kind of like keying the used car you just bought. It only damages the value of something you just paid money for; even if you think you got a good deal it is still a stupid thing to do.
Still - how would you feel as an employee of the acquiring company? Especially knowing that the newly-acquired employees are listening in? At best, awkward.
It's just complete verbal diarrhea and he should retract it (though the damage is mostly already done).
