Need help with how to handle this situation?

I used to hangout with these kids who would be known as "popular". But they turnt out to be the worst friends ever. Mostly because of my one best friend "bob" I'll say. He was actually a complete sociopath that nearly robbed me of my dignity and only wanted to use me. It was uneasy brekaing away from them near the end of last year. Over the summer i met new friends and now i have a much better life and emotional sanctity. But i never actually broke the bond between the last kids, i just stopped hanging out with them over the usmmer wen they stopped calling me becuz THEY had a party in my backyard while i was on vacation, because they felt awkward after they got in trouble with my parents. Now htis year im having a backyard party soon, and Bob keeps tyrign to ocme, and hes messaging me and stuff syaing y are you ignoring me and we used to be best friends. From what i learnt you should never interact with sociopaths nomatter what because it iwll just make it worse.. I really just wnat to tell him off though. What should i do?