If he is insulted and threatened by others, can I sue him in court?

The other party's abuse of you has violated your right of reputation, so you can sue him. As for his threat to you, if the circumstances are minor, it does not constitute a crime, but if it is for the purpose of extorting property, it constitutes a crime of extortion. Although not, if the circumstances are serious, administrative punishment may be given according to the regulations on administrative penalties for public security. But now it is a society ruled by law, and everything pays attention to evidence. When you go to court, you are asked to provide evidence. If you are advised to keep the evidence next time, such as secretly recording, if you are no longer harassed, you are advised to be generous. People who compete with villains are not necessarily smart. It is a gentleman's demeanor to laugh it off.

If you really want to sue without material evidence, I suggest you find someone to prove it. If there is no physical evidence, I suggest you not to sue. You can call the police and discuss things with them. The police uncle will not ask you for evidence, but will warn each other.