So at my school, there's a lot of sexual harassment, and I'm a victim. l was apparently accused of being the suspect though. I got yelled at by my mother and my stupid principal, because they don't believe that I'm a victim.
Explain in a rational and calm tone that they are simply wrong... "I'm sorry that you have misunderstood the situation, please excuse me while i <do something awesome!>." This is really sneaky, tried and tested... You both apologize and tell them off in one sentence. It's really important though that the person you tell this to is listening and you remain as calm and rational as possible. Look them straight in the eyes, without seeming mad or angry and shoot! Basically you show them that you feel no "guilt" because you are NOT guilty and when they see that, they quickly reconsider their standpoint because now it is they who are at fault.