How do you deal with a roommate that always wants to fight you when you didn't do anything wrong?

Well I have a roommate that is a bad roommate who's been giving me trouble since he moved in and he's been trying to fight me since he came here but I usually walk away because in the end I'm a bigger person than he is also it makes him look stupid trying get into fist fights when I just walk away from him yet he calls me a coward he should look himself in the mirror and see what kind of coward he is and of course it will take some time to get him to learn that he just looks stupid trying to start fights and to have everyone walk-in away from him even walking away from him doesn't help I'm needing a bit of advice on how to handle someone like that