What's the proper response to an accusation of date rape in the absence of hard evidence?

When faced with this kind of serious accusation within a social group, what is the proper judgment and course of action? If the victim seems believable, should the accused rapist be shunned or banned from the group? Should private warnings be given to group members? Does refusing to engage in any public discussion of the matter constitute silent assent to the crime? Or should judgment and action be reserved until further evidence comes to light?