What others think.....

This is my biggest problem at present. I know what he is and am handling that well but my problem is how he has convinced others that I am a bitter, psycho, bitch!!
I know that I shouldnt give two hoots what others think but I do. It's part of the injustice of it all...and I suppose recently learning that his girlfriend has taken him back despite me sending her explicit information regarding his cheating has reinforced to me that these people get away with everything. I hate that people who dont know you.. have a preconcieved idea of who and what you are based on what the narc has said about you without you getting a chance to have a voice yourself!!
I was triggered today as I saw a freind of his looking at me in a "funny" way which got me spinning with thoughts of him thinking I was a twisted individual and that no wonder the narc stayed out all the time and went with other women!! I even start to have conversations in my head practising how I would justify myself to them should they ever look at me that way again or say anything to me. Any advice?? I HATE this injustice but dwelling on it is not productive or helpful either!! Any nuggets of wisdom on this would be appreciated xx