Criticism is, in a sense, always a threat to our sense of identity in a way, which is why criticism MUST always be tendered very carefully. What do I mean by this? First of all it depends upon whom is the target of the criticism, and who is doing the criticizing.
So many times we hear someone say, "I'm just being honest," which seems to function as an excuse for venting sheer nastiness. We have all seen this.
Before we give criticism, we should check ourselves: Why are we giving this criticism, really? Do I really want to help this person or am I feeding my own ego, REALLY? Is this criticism I'm about to offer equally if not MORE applicable to myself, REALLY? What does one mean by CONSTRUCTIVE criticism?
There are ways to offer input (not to sound New Agey, but I prefer the term input rather than criticism) that do not risk resentment. But most important of all, when we feel we must offer "criticism" let us follow the advice of Jesus (whether he existed historically or not; or am I thinking of Confucius?) in making sure we have removed the log from our own eye before we seek to remove the speck from the eye of another.