What is the Muslim's duty when he hears a non-Muslim insult Islam and Muslims and transgress against Allah?

Whoever has the authority must prevent wrongdoers, or report them to the competent authorities. A Muslim must adhere to Islam and its ethics, for many who were astray were guided because they witnessed the good character of Muslims. Al-Shafi'i said: "He who admonishes his brother through his actions is a guide."