Coward and weak people use venom in their words to expulsate their own weaknesses and frustrations. Please ignore them, dont react to them. When and if confronted with such people think about something else in your mind, never take to your heart. If the relationship is extremely wicked than it is better not to ever see such people. Just pray for them quietly and do them any good if you are capacitated to do so and dont ever let them come near you.
Life is too short to be facing constant negative energy.
If you can dialogue and talk and settle fine, if not just do not deal with any such relation. This is the best approach. Nothing can ever happen then. Develop friendship with your own self, books, do other activities and communicte to your friends, than getting crippled in the war of words periodically. Be firm, dont heat up your mind and forgive them but dont try to change anyone.