What action can I take with a former employer?

last year i left my job in sales after a dispute with the president of a small distributor. He had gotten paranoid months prior to this because he thought i was looking elswhere for a job and was to leave the company. He thought i was going to go with the competitor and take some of the clients with me. It was far from the truth though i did gorw very unhappy witht the company. after we parted ways he aproached a former employee that had quit for the same reason i did and asked him to come back.his pitch for him to come back was.."now that we fired so and so(me)why dont you come back to the company"..for some reason he thought my other coworker left because of me which was untrue too. the ex coworker called and tol me what had happend and i was mad .i felt in a way he was slandering me. Recently i got a job offer from another company the does business with my past employer.