If he keeps pestering you with messages either ignore him or if they are using profane langauge report him. If he attacks you, you should have the full supprot of cav9d6 behind you which is 400k points compared to his tribe's 36k points. IF he can't see the reason behind it, talk to the baron, duke or head diplomat, of DASE. If they can't reign him in work with your tribe mates to organize a noble train and get rid of him.