Marvin, i totally understand your point, as i do everyone elses, but i feel zero regret.
And, at this point, I don't see any reason for you to feel regret.
I'll add that there is an argument that if someone entrusts something to us they are also entrusting us to do with it as we see fit unless told otherwise. Folks do this with personal letters all the time. A letter given to me by another is then my letter. Unless the sender states a condition of what can or cannot be done with that letter then ethically and morally I don't have an issue with acting responsibly with that letter based on my own ethical and moral standards, which is what the sender extended trusted over in the first place.
In this case it appears to me you acted responsible with what was given to you. Then the sender does, in my opinion, overreact as though you've broken a trust. Unless Fisherman asked that you not share his PM to you then I don't see an issue worth complaining about in this instance.