So, if a person who is desirable does something ‘bad’, we tend to look for a positive reason for his/her action, and whereas if another person who is not so desirable does the same action, he is looked upon in negative light. That person's 'bad intentions' or ego are blamed.
Especially during the times of quarrels, when one's judgement is polluted with bias, more misunderstandings are created.
A mind that judges under the influence of bias or ego always errs. So, be aware of this tendency of mind!