Ignoring him is the best option, returning the insult is lowering yourself to his level, keep in mind that we are all adults or we should be and an adult who spends his time insulting is a person who did not develop well mentally and his first defense would be to insult People are out of their minds, there are many ways to defend yourself without resorting to insults if you feel that the other person is attacking you, if it is because of the game that they insult you, just ignore it, it is a game and always keep that in mind.