This is an excellent piece and I very much agree with the spirit of it. However, I would say that some writers are thicker skinned, depending on personality, background, temperament, life experience, present mental state, etc.

Some writers (ie me) are much happier if people take the gloves off and are as ruthless as possible. But only, as you correctly point out, if they have been asked to do so, ie solicited criticism, delivered privately.