For me, you only have to read to them this Hadits:
Similarity Between The Fate of 'Ali bin Abi Thalib And Jesus
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Qaala Abu Abdirrahman (Abdullah bin Ahmad), "haddatsana Suraij bin Yunus Abu Al Harts, haddatsana Abu Hafsh Al Abbar 'an Al Hakam bin Abdul Malik 'an Al Harts bin Hashirah 'an Abu Shadiq 'an Rabi'ah bin Najidz 'an 'Ali qaala, 'qaala an Nabiyyi Shalallahu 'Alaihi wa Sallam, "Fiika (in thee) matslu min 'Iisa (there is similarity with 'Iisa), abghadhatHul Huudu (who is hate by Jews) hatta (so) bahatuu (they despise) ummahu (his mother), wa ahabbatHun (and being love) nashaaraa (Christian) hatta (so) anzaluuhu (they put him) bil manzilahillatii (in a place) laisa bihi (not meant for him). Tsumma qaala ('Ali) 'yahliku (will be doom) fiyya (by me) rajulaani (2 kind of person), muhibbu (they who love me) mufrithun (to the extreme) yuqarrizhunii (they praise me) bimaa laisa fiyya (in something that aren't exist on myself), wa mubghidun (and who hate me) yahmiluhu syanaaaaanii (so that their hate on me) 'alaa an yabhatanii (will make them to despise me). (HR.Musnad Imam Ahmad no.1376,declared as Hasan by syaikh Ahmad Muhammad Syakir).
Qaala Abdullah bin Ahmad, "Haddatsana Abu Muhammad Sufyan bin Waki' bin Al Jarrah bin Malih, haddatsana Khalid bin Makhlad, haddatsana Abu Ghailan Asy Syaibani, 'an Al Hakam bin Abdul Malik 'an Al Harts bin Hashirah 'an abu Shadiq 'an Rabi'ah bin Najidz 'an 'Ali bin Abi Thalib, qaala, "Rasulullah Shalallahu 'Alaihi wa Sallam called me, then he said, ... (Just as hadits no.1376) but there is another sentences which is "Alaa innii lastu bi nabiyyii (Know that I'm not a Nabi) wa laa yuuhaa ilayya (and there is no revelation come unto me), wa laakinnii (and but I am) a'malu (doing good deeds) bi kitaabillaahi (in All Qur'an) wa sunnati nabiyyihi (and Sunnati Nabiyyi) Shalallahu 'Alaihi wa Sallam maastatha'tu (in my ability), famaa (then whatever) amartukum (I told thee) min thaa'atillahi (in telling to obey Allah) fahaqun 'alaikum (it is the truth for thee) thaa'atii (to obey me) fiimaa (in whatever) ahbabtum (whether it is that you love) wa karihtum (and what you hate).(HR.Musnad Imam Ahmad 1377, Majma' Az Zawa'id Al Haitsami chapter 9:133, declared as Hasan by syaikh Ahmad Muhammad Syakir).
The Punishment Of Syi'i Or Alawi By 'Ali bin Abi Thalib Radhiyallahu 'anhu
'an Ikrimah, that 'Ali Radhiyallahu 'anhu had burned Murtadin (apostates). The news spread to Ibn Abbas Radhiyallahu 'anhu then he said, "I will not punish Murtadin with fire. Because Rasulullah Shalallahu 'alaihi wa Sallam had said, 'Don't punish humans with Allah's torture (fire).'
(Shahih Al Bukhari, Abu Daud 4351).
This was what happen with the followers of Abdurahman bin Saba'(Jews) followers.
Abdul Qadir bin Thahir Al Baghdadi said in Al Farq Bainal Firaq page 37, "The Rafidhah of Kufah were known of their treachery and stingyness, so they became a bad example for this." Always said by people "Fulan is more of traitor rather than Kufah people, Fulan is more stingy than Kufah people."
What is known (Masyhur) from them were:
1. After the killing of Ali bin Abi Thalib, they Bai'at his son Al Hasan bin 'Ali radhiyallahu 'anhu. But then they did treacherous acts against him in the road of Al Madain. Al Hasan radhiyallahu 'anhu was stabbed in the stomach by Sinan Al Ju'fi until he was fell from his horse.
2. They sent a letter to Al Husein bin 'Ali radhiyallahu 'anhu and invited him to Kufah. When they were arrived at Karbala, they did treacherous acts against him and became 1 hand with Ubaidullah bin Ziyad became 1 hand to fight him, which caused the killing of Al Husain and all of his families.
3. Their treacherous acts to Zaid bin 'Ali bin Al Husain bin 'Ali bin Abi Thalib after they gone out to fight Yusuf bin Umar, and then they released their BAI'AT and handed him to the enemies, which got him killed in that war.
Bidayah wan Nihayah by Ibn Katsir(7/274 and 280) , Al Bidayah by Ibn Katsir(8/149), Siyar A'lam An Nubala' by Adz Dzahabi(3/280), Al Bidayah by Ibn Katsir (9/273), Siyar A'lam An Nubala' by Adz Dzahabi(5/389).
Assalamu'alaikum wa rahmatullahi wa barakaatuh.
Assalamu'alaikum wa rahmatullahi wa barakaatuh.