What should I do concerning a Christian who insulted the religion of Islam; should I insult his religion or not? And is it permissible to insult Satan?

Cursing the religion of Christians, if the intent is the religion of Christ (peace be upon him) before its distortion, is not permissible. However, cursing the falsehoods they are currently upon is permissible in principle. But a Muslim considers the consequences of actions. If cursing would lead to discord or to them cursing the religion of Islam, then it is not permissible. It is better for a Muslim to accustom his tongue to refrain from obscenity and cursing in general, as the Prophet (peace and blessings of Allah be upon him) said: "The believer is not one who slanders, or curses, or speaks obscenely or indecency." And as he said to Aisha (may Allah be pleased with her) when she cursed the Jews: "Be gentle, O Aisha, for Allah does not love indecency or being indecent."