At the moment when a person insults you, his main goal is to provoke a response from you. For your part, you can discourage and disarm him by remaining absolutely calm and simply agreeing with his words. And after that, thank him for taking the time to look for your shortcomings and point them out to you. He definitely does not expect such behavior from you and he will understand that it is simply useless to continue doing this.
The method can also help to get out of the situation with dignity when you answer the interlocutor with the same phrases, for example: “So what?”; "So what?" etc. Such a reaction of yours will allow you to remain calm and will infuriate your interlocutor.
An unexpected reaction to his words on your part will also help to disarm the interlocutor. For example, if you take and laugh at the moment when he insults you.
Cool insults for all occasions

In any case, try at such moments to learn how to behave competently and not get involved in mutual insults. Try not to let your opponent get what he is trying to achieve by creating this situation. Of course, it’s not easy to pull yourself together, but this is what will help you get out of the situation as a winner.