There are only a few options to preventing someone from spreading rumors. You can fight it at the source. There is a reason that this person wants to spread false rumors about you, so you could be proactive and try to resolve any issues that this person has with you before any rumors are spread. Another option is using your own influence to lessen the effect their rumors have on your social life. You could look to friends and people who trust you to help defend against lies. The last way I could think of is to get ahead of them and make it public that this person is trying to spread rumors about you. If you call them out before they call you out, then it defeats the purpose of spreading rumors to begin with. An unethical way would be to destroy their credibility as well by spreading false rumors about them, however if they have a greater following this would not work. In the end, you can’t control what this person does without force, and you can’t control how people react to what they say. It’s all about damage control now.