this is when you want to be tough

he is clearly bullying you. tell him "Fxxx Off" or something in that nature. Obviously I am just kidding. whatever style you prefer, you'd better be firm. tell him that 1) you are not responsible for the actions of your tenants. 2) if you have to let your tenant go, you will be breaching the contract, therefore need to pay the tenant for damages. 3) if he really want this thing solved, he can rent your apartment, but he has to pre-pay 1-year rent. blah blah blah.