He could have also been professional and only stated that the employees statements are generally false, and left it at that.

The response went into far too much detail. Wrongful termination lawsuits happen all of the time, defamation can be found when any term you use can not be evidenced.

A pro would have either ignored this AMA or issued blanket, definable statements, such as "You were fired for performance related reasons."

In the sense that he seems to have successfully trolled a CEO, yes, he "forced" the issue.

No. If anything it's up to the company leadership to be tactful, level-headed, and importantly, magnanimous in the face of petty slights and provocations -- like those of the severed employee, in this case.

And that's what's so tragically stupid about this whole thing -- what happened at the outset (the employee's remarks in a public forum) was a very little thing. And what did Yishan do? He want out of his way to make it a big thing. It's like he sees a fire in the wastebasket, and his natural instinct is to throw more oil on it.