This is not to say I have always been the best at receiving criticism graciously, especially right off the bat. Criticism stings, especially when it comes from an angle you weren't expecting (or worse, were secretly dreading but hoping nobody would notice). It's hard not to bristle and be defensive when someone points out, however gently, that you've messed up somewhere. And I have sometimes been guilty of arguing with my critics, when I should have just said "Thanks for your comments," and moved on.
Of course, even criticism which is intelligently voiced and meant to be helpful isn't necessarily valid. Sometimes the critic has read carelessly and missed the point; sometimes the critic simply dislikes or is ignorant of the genre in which the story is written. Every criticism has to be weighed by the author in his or her own mind, and either used or discarded according to its perceived worth. But the point I think O'Shea makes most cogently is that criticism is necessary and important to every author's development, and that if we are unwilling to hear anything but praise or the very gentlest suggestions for improvement, we are never going to be authors in any meaningful sense of the word at all.
My primary reason for not liking criticism -- I confess -- is that I am lazy. I don't like having to revise things that I've revised umpty times already. It's frustrating enough when I realize on my own that a chapter or a story I thought was finished still needs work; it's twice as frustrating when somebody else points out a flaw or inconsistency or weakness I hadn't noticed and I realize that it needs to be changed too. But laziness is my problem, not the critic's, and I haven't any right to take my frustration out on someone else who is simply pointing out the truth. Particularly if I asked for their honest opinion, and they did me the courtesy of taking me at my word.
And that's the last point I'd like to make. If you don't really want criticism, or if you only want a certain select kind of criticism, don't ask people to give you their honest opinion. If you don't really trust a particular person's judgment or think they have a bias that would make them unfit to judge a certain story, don't ask them to be your beta-reader on that story. But if you have asked for honest opinions and you have asked a certain person to tell you what they think, don't be surprised if some of the comments aren't phrased exactly the way you'd like or if they tell you things you're not particularly happy to hear.
If you privately decide that the critic is an idiot or a bigot and their criticism isn't worth squat, that's your business. But it's pretty unfair to tell them to their face that they're an idiot or a bigot and their criticism isn't worth squat after you asked for their opinion and they gave you what you asked for. As a beta-reader I've been stung by this kind of response a few times now, in spite of making every effort to be tactful in my criticism and to give the author a fair chance, and it really makes me not want to read or comment on other people's work at all.