This type of thing happens on most forums (including this one). People come to the site looking for a particular answer, when we tell them that they have made a mistake somewhere else, they feel slightly insulted because we have demonstrated that we know more about the subject then they do.
Also, people pride themselves on their knowledge -- so when the experts give them a reality check and say, "Hey, your doing this wrong.", they get annoyed.
Or something like that
Sounds stupid, but it happens. I get insulted in the ASP and Other forums sometimes.