The word "criticism" and its connotations...Writers often conflate the idea that criticism and negative criticism are the same thing, often forgetting that there is also such a thing as positive criticism. I would dare to bet that many new writers think that "positive criticism" is either an oxymoron or means that positive criticism is just negative criticism said in a nice way.
Positive criticisms are notes readers or editors will write in the margins like, "This is a powerful sentence," "I loved the way you brought all the conflicts together in this one paragraph," "Nice imagery..." Positive criticism of this sort is both nice to hear and might be instructive as to what the reader or editor thinks the writer did well—and the writer can learn a little something about writing from these bits of praise sprinkled throughout a manuscript. But in the end, it is the negative criticism that writers should listen to the most.
Having one's work edited or critiqued should not devolve into an adversarial relationship. Oh sure, editors can be wrong, the criticism can be irrelevant, and ultimately, when the writer is alone with the edited manuscript she is free to reject everything the editor has indicated. But it's not a good idea to fire back a heated response to the editor—ever.
It's those little poison darts that get us where it hurts that writers should pay attention to and consider thoughtfully. This is where writers will learn the most about writing; this is where a writer's skill and the book in question will improve.
As a writer, of course I read all the positive reviews that have been posted about my work. Praise is nice to hear. But I also read all the negative reviews, and once I get over the immediate anger and defensiveness that a negative review automatically engenders in me, I take the negative review into consideration. Amid all the positive reviews about one of my book series, one particular reader went out of his way to essentially say the same thing about each of my books, giving them a one-star rating on Amazon. Ultimately, while there was some merit about what he said about my main characters (they cry a lot), I gleaned that he didn't like the concept of my stories, which must have gone against his own idea of what characters like mine should strive for, and so he struck out in anger in language that was simply incendiary. Eventually, I was able to shrug off most of his criticism, but the thing about my main characters crying a lot was true. Another negative review had to do with my very long, very detailed, very dense fantasy novel. A different reader, not the mean one, said it was the kind of book a person should read if he or she is stuck in bed with the flu. The reviewer was not mean-spirited in the least, and his comment was clever. This was negative criticism about whether or not my novel was boring. I have no problem realizing that some readers might find a 350,000 word novel a little too detailed for his tastes. In fact, one of my beta readers whose opinion I respected (he was also my boss) said that I should cut the content of the fantasy novel by 75 percent. Ouch! In this case, however, I didn't take his advice. I believe that I had good reason to keep what I wrote, and so I thanked him for reading the manuscript and carried through with my plans for this mammoth book.
That is why it is important for writers to listen carefully to the negative criticism from editors and beta readers and to think strongly about revising what the editor and readers have said before the book is published.
A whole other consideration about the fear of criticism, however, is that writers should not write to avoid negative feedback, should not avoid offending anyone, because there will always be a certain number of people that will dislike a book, be offended by the content of a book, or find something wrong with it. Writers should always write to please themselves first, but that is a different topic.