Doesn't defamation of a public figure require "actual malice"? If so, doesn't the CEO's admission in writing that "I believe your post was made in good faith" severely undermine any claims of defamation?
Even if he is found to be a public figure, I believe the "actual malice" standard would be determined by the defendant's knowledge and regard/disregard for the truth at the time of writing -- meaning it doesn't matter whether the CEO later believed the defamatory statements were made in good faith.