I was posed this problem by someone in a very highly ranked research department in one of the social sciences (not Philosophy, not Madison), and post with permission.

Graduate Admissions Committee for the department in question is deciding whom to admit. For said discipline, as for several others, there is a website on which potential students gossip share information about the departments to which they are applying, and many do so anonymously. However, many such students say enough about themselves that if you are in possession of their file (as graduate admissions committee is) you can identify them with near, and in some cases absolute, certainty. One applicant to said department behaves on the website (under the supposed cloak of anonymity) like… well, very badly, saying malicious things about departments he has visited, raising doubts about whether he is honest and the kind of person it would be reasonable to want other students to deal with, and generally revealing himself to be utterly unpleasant.

Question: is it wrong for the GAC to take this information about the applicant into account when making a decision? Secondary question: does it make a difference to your answer that the department is in a private, not a public, university?