Is a Muslim held accountable for reviling and cursing Jews and Christians?

It is not permissible to revile or insult a non-belligerent disbeliever. Whoever does so is sinful and owes a right to the disbeliever. As for cursing a specific disbeliever, there is a difference of opinion, and the apparent view is that it is not permissible because their state at the time of death is unknown, and they might embrace Islam. However, cursing disbelievers in general, or those among them who died upon disbelief, is permissible. Foul language is not characteristic of a Muslim. Allah Almighty commanded Moses and Aaron to speak kindly to Pharaoh, so others are more deserving of gentle speech.