Ithnaa Asharis? [updated.]

Q. i would like to ask you if Ithnaa Asharis are kaafirs? They do slander the Sahabah, the Umm-al -Moamineen and they do consider us kaafirs. They also do alot of Shirk like saying: " Ya Ali", "Ya Hussain",etc.

Calling out their names is not proof that they worship them together with Allah so it cannot be called shirk; nor do we have to reciprocate their takfir of us; nor does slander of the Sahaba entail kufr but only fisq, except qazf of `A'isha, which is kufr. However, some of the Shi`as are kafir according to the conditions detailed below.
The Ithna `Ashari (literally, "Twelvers") are the largest group of the Shi`a and are also called Imamis after their doctrine that their twelve Imams are immune from sin (ma`sum). The Shi`a are also known as Rawafid, or Rafidis, or Rafida, although strictly speaking the Rawafid are only one extreme group among them. However, if we should take Ruhullah Khomayni as an accurate representative of the Ithna `Asharis, it would seem that most of them today are actually Rafidis although they do not show it at all times, but Allah knows best.
Below is an answer from Imam Muhammad Ahmad Rida Khan Barelwi, given in his Fatawa al-Haramayn (Waqf Ikhlas offset reprint p. 10):

Question Three: What is the Status of the Rafadah?

Answer: The Rafidi, if he prefers Amir al-Mu'minin `Ali to the Two Shaykhs [Abu Bakr and `Umar] - Allah be well-pleased with all of them - is an innovator (mubtadi`) as stated in al-Khulasa, [al-Fatawa] al-Hindiyya and other books; but if he denies the validity of the Imamates of Abu Bakr and `Umar or the validity of the Imamate of one of the two, then the jurists (fuqaha') declared him kafir while the theologians (mutakallimun) declared him an innovator - and the latter ruling is the more precautionary one. If he claims (1) to correct Allah Most High [i.e. in sending the Revelation to the Prophet rather than `Ali] or (2) that the existing Qur'an is defective or (3) that the Companions or anyone else altered it, or (4) that Amir al-Mu'minin [`Ali] or any other of the pure Imams is better than the Prophets in the sight of Allah - upon them all blessings and peace - as openly claimed by the Rafadah of our regions [India] and as stipulated in our time by their Mujtahid - he is definitely a kafir and the ruling that applies to him is that of apostates, as stated in al-Hindiyya quoting the Zahiriyya and in al-Hadiqa al-Nadiyya and others of the Fiqh books. We have enlarged upon this question in our epistle _al-Maqala al-Mufassira `an Ahkam al-Bid`a al-Mukaffira_.

Q. Also sir, i wish to ask you about Mufti Ebrahim Desai of South Africa, is he within the Ahlus Sunnah?

Yes he is, insha Allah. I have asked him to take back or explain his fatwa that Barelwis are outside the fold of Ahl al-Sunna and await his answer. The Barelwis are part of Ahl al-Sunna generally speaking, just as the Deobandis are part of Ahl al-Sunna generally speaking. As for individuals, then each case is examined on its own merits.

you had stated that slandering the companions does not make one kaafir. But sir, according to Imam Tahawi in his book " Al Aqeeda ", he said: "We love the Companions of the Messenger of Allah but we do not go to excess in our love for any one individual among them nor do we disown any one of them. We hate anyone who hates them or does not speak well of them and we only speak well of them. Love of them is a part of Islam, part of belief and part of excellent behaviour, while hatred of them is unbelief, hypocrisy and rebelliousness. "

The words "hatred of them" means "hatred of all of them" because Allah Most High praised their generality. To hate some of them is nifaq because the Prophet said so precisely in relation to `Ali, Fatima, al-Hasan and al-Husayn, Ahl al-Bayt in general, Abu Hurayra, and the Ansar. And Allah knows best.

Also sir, even if we were to assume all Ithnaa Asharis are not kaafirs, and are just innovators, in which there is no doubt. Then does their innovation amount to kufr or not?

When it meets the criteria of kufr in specific cases then it amounts to kufr, otherwise not.

Also sir, is it true that they doubt the authenticity fo the Qur'an, as was proved in the book Faslul Khitab fi Tahrif Kitab Rabb al-Arbab by Husain al-Nuri al-Tabarsi.

Yes, you notice this extremism and blatant apostasy in their Ulema, and to Allah Most High is our return.

could you also tell me what Imam Ashari and Maturidi had to say about the Ithnaa Asharis and cursing Sahabah?

To my knowledge it does not differ from what was stated already except that the last words of the Ibana attributed to al-Ash`ari are that whoever disparages a single Sahabi, we cut off our ties with him. I.e. we consider him at the very least an innovator in the Religion.

From what I know, the Ithna-Ashari Shias believe that the Prophet Muhammad (SWAS) is the best of creation, then Imam Ali (as), and that Imam Ali(as) is better than all of the other Prophets(as).( They give the other Imams the same status with regard to the previous Prophets(as).) I'm wondering what is the daleel for the view that believing this takes one outside the fold of Islam. I'm puzzled as to why should that be so, if the person in question sincerely believes in all the articles of faith, and fulfills the five pillars?

The problem is this is an article of faith as stated verbatim in the `Aqida Tahawiyya Par. 98: "We do not prefer any of the saintly men among the Community over any of the Prophets but rather we say that any one of the Prophets is better than all the awliya' put together." The proof is that Allah Most High { never sent a Messenger except to be obeyed} (4:64) while there is no obligation to obey `Ali nor sin in not obeying him (sa). Further, there is Consensus in the Umma that Nubuwwa is more special than Wilaya and that Risala is more special than Nubuwwa. See also Jawharat al-Tawhid and its commentaries as excerpted in my post on msa-ec "Best of Creation" . And Allah knows best.