The trick is to make sure you (and those around you) understand the difference between a constructive criticism of someone’s creative output and a flat-out assault against someone’s character. The latter is useless — it’s petty and nearly impossible to act on. The former can (and should!) be helpful and give guidance on how to improve.
Giving feedback well is a lot harder than "don't attack the person."
I find that feedback that wasn't well-received was rarely an assault against someone's character. That is, even feedback on the output can be taken unwell (as in the example above).
