All of this might have been avoided had the "mildly critical" email not been sent. I have no idea what your comment was, nor does it matter, however you are now dealing with the consequences of your action.
While you and I have every right in the world to share our opinion, that doesn't keep us immune from bullies and vengeful people.
Sounds like this was a lesson learned in what NOT to do if you want to criticize someone.
What did my mother always say: "if you don't have something nice to say about someone, don't say anything at all."
Life will go on and you will survive things that will make this pale in comparison.
