I can easily overlook any flaw in any person. But I cannot be too ready to do so when, apart from being flawed, the person is also blatantly ignorant about that fact that he was flawed.
I emphasize the word "blatantly". I can understand that everyone has his "learning curve", and therefore being ignorant when he has just been told of his flaw was acceptable. But it becomes a problem when repeated explanations fail to inform him of this fact. This type of people will insist on believing that 1 plus 1 equals 3 for months and years and resist all attempts by others to correct them. And the unfortunate truth is that they exist.
So, I think that we can perhaps learn a great deal by looking at people with inferior abilities positively. But this only applies to the majority of them. A minority would better be left to be corrected by the flow of time.