The mistake Mr. X. made here was not about caring about his job or even criticizing his employer. He contacted an outsider, with his company's email server, ostensibly on their behalf. At bigco, you just can't do that folks. Everything that leaves corporate walls must be vetted by legal, (and probably marketing too). There are lists of 100's (maybe 1000's by now) of innocuous seeming words that you just can't use. Language, nationality, gender, and racial issues all must be considered.
Like it or not, at Bigco International, everything is a press release.
Personally, I would have given the guy a warning. What he said was quite harmless and almost certainly common knowledge, but we don't know the whole story here. He may have been warned before, or AA burned by this type of thing before or both. Its unfortunate, but understandable. In the name of tolerance and acceptance, we've built one of the most intolerant and litigious societies ever. This is just one of the many sad side effects.