Except if the CEO knowingly made a false and damaging statement about an employee in public, he could be sued for libel. It's unlikely that a CEO would be stupid enough to do that.

The statement by the CEO seems 'stupid enough' already. It has qualifiers that could make this a wrongful termination, defamation, or other lawsuit.

If it's performance related, that's all that you should state. Defining and qualifying "much" is difficult.

It's probably not best to tell the public that inappropriate interview questions have been being asked ~for a while~.

This response stinks of a small company that could have definitely benefited from using a PR statement instead of a posting from the CEO.

It took a public outcry for Reddit to ban kiddie porn. This is not a site with a history of caring much about such concerns.

Unlikely. There's a clear distinction between being fired and being laid off and so the disagreement is about a matter of fact, not opinion. More likely the guy started an AMA without thinking it through, then lied to save face when someone asked why he was let go.