Something that has always kind of surprised me is the number of people who don't seem to be able to reason out the difference between the kind of criticism people should be able to graciously accept and the kind that the offerer of it has no business expecting the target of it to graciously accept.
Not all criticism is equal. I'm perfectly fine with what I see as "appropriate" criticism, and that is criticism by someone like a supervisor in the work place, a teacher/instructor in the classroom/course setting, or criticism I request if/when I asked someone for their thoughts on one thing or another.
I'm not in the least bit interested in the criticism of someone who appoints himself critic, advice-giver, input-offerer, etc. on anything I do or am in my non-school or non-work life or on anything on which I have not requested someone's opinion.
A good part of the time people who "have opinions" about how/what someone else should do things are people who don't have a clue about what the other person is dealing with; and people who, if they faced all the same factors that the other person does would do the exact-same thing, would do things the exact-same way. Then, too, there are those times when two people are so different, what one does that's right for him wouldn't be right for the other person. So either way, unsolicited criticism (outside work or school and offered/imposed by someone whose role is not supervisor or teacher) comes from people who, for one reason or another, don't know what's they're talking about (no matter how superior, informed or educated they imagine themselves to be).
Good interpersonal skills tell people who have them that unsolicited, inappropriate, criticism isn't acceptable. Good reasoning ability tells people that they can't/shouldn't have an opinion about someone else because they can't have all the information about that person's inner or outer situation, and therefore are not capable of offering an opinion based on everything that goes into what someone does. So, people who directly express criticism of other individuals lack interpersonal skills and/or sufficient reasoning skills; and therefore, are most often people who really aren't in the position of knowing any better than the other person what that other person should/could be doing. The ego of people who feel free to offer unsolicited criticism is bigger than it ought to be when they appoint themselves critic of others, and respect others so little that they believe their own opinions are superior.
So, in the school or work setting (or where someone asks because he values the input of the other person), only a blockhead would have trouble accepting criticism graciously. Other than that, it's those who criticize who are most often the clueless blockhead.