Often it is not the "Facts" but "Wrong Assumptions" that makes us misunderstand people. Assumptions can be dangerous,to an extent you can't even imagine when you begin.
Without ascertaining the truth,the former depends upon his own views and forms a wrong opinion of that person. So while dealing with that person,these demerits which are the products of imagination and guess-work start showing it in the former's attitude. The only way to deal with it is to relax,believe and if not,then rely on facts rather than setting up pre-assumptions and creating a polluted image of a person who might be innocent or atleast not the type your imagination has calculated. These assumptions are fatal as they do not limit themselves to one person only but spread across defaming and degrading others. Be careful of your mind assuming people and their actions.