One person keeps calling me stuff that im not. I have defended myself before but he still insists on calling me names and others. He says this publicly. Should I still keep defending myself if I believe that there will be of no use in defending since he keeps on insisting

You are not obliged to stay silent under a fabrication, so say plainly to whoever it reaches that this is not true and leave it at that. Once you have cleared yourself, turning away from him is better than answering him again, and do not answer him by spreading his faults and transgressing against him. Make dua to Allah and He will suffice you.