I have to say: If you are writing you are putting yourself out there.
Some will love it, some will hate it. If you can't deal with the criticism you should not put yourself out there.
Why the hell are his friends outraged when a bit of criticism is uttered?
That should be a non issue. This threat is harmless. Nobody here went full Marcel Reich-Ranicki on him.
He should be professional enough to just shrug it off. That he is not, is worrying.