Here is the chain-smoking Ayatullat Khoie of Najaf, the teacher of Sistani (who can’t even speak proper Arabic nor lead a single prayer with adequate Tajwid which even 5 years old non-Arab Sunni kids manage). He was loyal to Saddam and at the same time preached that cursing Sahabah, backbiting Sunnis, and slandering them behind their back is permissible. He was Abu Smokey and Abu Taqiyyah in one person.
A question posed to Ayatullat Khoie:
Questioner: Is it permissible to spread lies about a heretic or a promoter of deviance (i.e., Sunni) during the time of argumentation against him, if that lie serves to refute his proof and nullifies his false claims?
Answer by al-Khoei: If this refutation stops him, then yes.
Source: Sirat al-Najah, Vol. 1, P. 447, by Abul-Qasim Khoie
Another similar fatwa straight from the official Khoie website that is run by his Ayatullat mafia clan:
السؤال : وهل يجوز سب أهل البدع والريب ، ومباهتتهم والوقيعة فيهم ؟
الجواب : إذا ترتب ردع منكر على تلك ، فلا بأس
Question(er): Is it permissible to insult the people of innovation (Sunnis and all non-Twelvers) and to defame and slander them?
Answer (by al-Khoie): If deterrence of evil results from that, then there is nothing wrong with that
Sunni Islam in comparison (Islamqa):
It is not the attitude of a Muslim to insult others, slander them and impugn their honour. The Prophet (peace and blessings of Allaah be upon him) said: “The believer is not given to cursing, slandering or obscene and foul speech.” Narrated by Ahmad, 3948; al-Tirmidhi, 1977; classed as saheeh by al-Albaani in Saheeh al-Tirmidhi.
The Prophet (peace and blessings of Allaah be upon him) told people not to insult a Jew who deserved to be insulted, and he said that the reason for that is that Allaah does not like obscene talk.
Al-Bukhaari (6401) narrated from ‘Aa’ishah that the Jews came to the Prophet (peace and blessings of Allaah be upon him) and said: “Al-saam ‘alayk (death be upon you). He said: “Wa ‘alaykum (and also upon you).” ‘Aa’ishah said: “Death be upon you, may Allaah send His curse and wrath upon you.” The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Take it easy, O ‘Aa’ishah! You should be kind and gentle, and beware of harshness and foul speech.” She said: “Did you not hear what they said?” He said: “Did you not hear what I said? I responded to them, and my du’aa’ concerning them was answered, but their du’aa’ concerning me was not answered.”
It says in al-Mawsoo’ah al-Fiqhiyyah (24/142):
For a Muslim to slander or insult a dhimmi (a non-Muslim living under Muslim rule) is a sin, and a Muslim is to be punished if he insults a kaafir. Al-Shaafa’i said: It makes no difference if he is alive or he is dead and is known to have died in kufr. Al-Buhooti, one of the Hanbalis, said: The punishment is because transgressing the limits set by Allaah. End quote.
The point is that whoever defends the honour of a kaafir, by refuting what is said about him wrongfully, is doing no wrong, in fact he is doing the right thing. It is not the way of a Muslim to slander people’s honour. If he also tells him to stop slandering and insulting others, he is doing good and will be rewarded in sha Allaah.
And Allaah knows best.