A few narrations from the Salaf regarding Backbiting Ahlul-Bid'ah:
Zaa'idah bin Qudaamah said: "I said to Mansoor binul-Mu'tamar: "If I was fasting, is it allowed for me to degrade and belittle the sultaan?" He said: "No." I said: "So can I degrade and belittle ahlul-ahwaa'?" He said: "Yes."
[Ibn Abeed-Dunyaa in Al-Gheebah (pg.83): hasan]
Al-Hasan al-Basree said: "There is no gheebah of ahlul-bid'a."
[Hasan: Al-Kafaayah of al-Khateeb (pg.43) and Ibn Abeed-Dunyaa in Al-Gheebah (pg.88)]
Ibraaheem an-Nakha'ee said: "There is no gheebah of a person of bid'ah."
[Al-Laalikaa'ee (1/140), Sunan ad-Daarimee (1/120)]
Sufyaan bin 'Uyaynah said: "A person of hawaa' in the Deen, there is no gheebah of him." [Mukhtasarul-hujjah of Nasr al-Maqdisee (pg.538)]
Shu'bah binul-Hajjaaj said: "Come let us backbite for (the Sake of) Allaah (Subhaanahu wa Ta’aala)."
[Saheeh: Al-Khateeb in Al-Kafaayah (pg.52), Aboo Nu'aym in Al-Hilyah (7/152)]
Aboo 'Abdillaah Muhammad bin 'Abdillaah al-Andaloosee, Ibn Abee
Zamaneen [d.399H]: "And Ahlus-Sunnah did not cease to degrade and insult the misguided ahlul-ahwaa' and prohibit from sitting in their gatherings, and fearing their fitnah, and informing about their innovation, and they did not see that as gheebah nor slandering of them."
[Saheeh: Al-Khateeb in Al-Kafaayah (pg.52), Aboo Nu'aym in Al-Hilyah (7/152)]
