Okay, well, I can't do anything about lying outside of per se defamation. so if he calls you a pedophile or something I can respond to that. I still wouldn't suggest reposting the same thing over and over in replies everywhere he goes because that does meet the definition of harassment.

All I see from him are standard insults, and assessments about your character and intentions. Even if untrue, those aren't really actionable. The best I can do is require both of you to not reply to each other's posts or comments if that is what you would prefer.