First of all, calm down. Don't splash out on the person your anger or the anger, even if he himself, unwittingly, brought you to this state. Understand that aggression is not the best way, even from a similar situation. If you pull the angry off-leash even on the person with whom you do not want to further communicate, facilitate you it will not bring.
Do not try to behave so that the person with whom you want to communicate, there is a disgust for you. Here we have in mind: rude attitude, inappropriate behaviour and any attempt to cause a person to experience a you dislike. You are mistaken if you think that the disgust that man will cause him to cease to look for ways of communicating with you, and you suddenly feel the most happy, because get rid of the problem. No, I won't, and the place of one problem another one will grow – remorse.
Politeness – that's your main helper. Be polite as you are polite in communicating with their parents, friends and other people with whom you communicate in everyday life.
Honestly to tell the person that it is unpleasant to you, and fellowship with him irritates you, even if it all will be posted in the most polite manner, it is still not easy. If you have a fairly strong character, strong nerves and a bit of acting, then you may be able to do it.
If you are not so honest, then try to use a different method. When this man wanted somewhere to spend time with you, tell them you are busy with work and next month just can not even an hour to devote to walking or sitting in cafes. If you see each other in a circle of friends, try to choose a place away from that person, communicate with other people, while in the side from the unpleasant person. In the end, the person will bother to chase you, and he will pay attention to someone else.