I'm Not That Toxic Person in Your Past!

Just as a verbal murderer condemns people for the group to which they belong, a murderer will often throw poison verbal darts at someone who reminds him of someone who did him wrong.
Most of the time, however, people who dislike someone don't know the reasons why. If you ask them what that person did to them to arouse such disdain, they will be at a loss for words.
Unfortunately, if people have had a series of bad personal relationships (in which they have been cheated on repeatedly, for example), they often might be very suspicious of you and perhaps believe that you are cheating on them as well. Even if you never give them any cause to think that you desire someone else, they might keep insisting that you have been unfaithful.