Is it permissible to curse or revile a non-Muslim for any reason or no reason?

It is permissible to curse and revile the polytheists and their deities, based on the Almighty's saying: "Indeed, the polytheists are unclean," and "So the curse of Allah is upon the disbelievers." And based on the saying of the Messenger of Allah, peace and blessings be upon him: "May Allah curse the Jews and Christians, for they took the graves of their prophets as places of worship." However, we are forbidden from reviling their deities if it leads to them reviling Allah the Almighty, based on His saying, Glorified be He: "And do not insult those they invoke other than Allah, lest they insult Allah in enmity without knowledge." So, if it is feared that the disbeliever might revile Islam, or the Prophet, peace and blessings be upon him, or Allah, the Mighty and Majestic, then it is not lawful for a Muslim to revile their crosses, their religion, or their churches.