What should a person do regarding those who insult the Companions in the Holy Mosque of Mecca, and is he sinful if he leaves them to their own devices, taking into account that they use the Almighty's saying, "To you be your religion, and to me be mine" as a proof?

A Muslim is only required to advise and inform the authorities, as Allah Almighty says: "So remind, [O Muhammad]; you are only a reminder. You are not over them a controller," and His saying: " incumbent upon you is only to convey." So, whoever among you sees an evil, let him change it with his hand; if he is unable, then with his tongue; and if he is unable, then with his heart—and that is the weakest of faith.