Quick question, if we're to be treated as Muslims according to al-Khu'i, why is it allowed according to Khu'i to backbite us and cause us harm through scheming and tricking us?
ثبت في الروايات(1) والأدعية والزيارات جواز لعن المخالفين ، ووجوب البراءة منهم ، وإكثار السبّ عليهم ، واتّهامهم ، والوقيعة فيهم ـ أي غيبتهم ـ لأنّهم من أهل البدع والريب(2). بل لا شبهة في كفرهم ، لأنّ إنكار الولاية والأئمّة حتّى الواحد منهم ، والاعتقاد بخلافة غيرهم ، وبالعقائد الخرافية كالجبر ونحوه يوجب الكفر والزندقة ، وتدلّ عليه الأخبار المتواترة الظاهرة في كفر منكر الولاية ، وكفر المعتقد بالعقائد المذكورة وما يشبهها من الضلالات
He also said here that denying one of the Imams or believing in the Imamah of other than the twelve no doubt necessites Kufr. How'd he make a switch and become a Takfiri here?
Or is backbiting and plotting against muslims a teachings from the teachings of Shiasm?
As for not doing Qada' for the prayers missed as a Sunni after converting to Shiasm, Khu'i says it's because the condition of being a Sunni is literally a lot worse than missing some prayers:
إنّ الحال التي كنت عليها أعظم من ترك ما تركت من الصلاة
Then he follows it by saying:
نعم قد ثبت حكم الإسلام على بعضهم في بعض الأحكام فقط تسهيلا للأمر ، وحقناً للدماء
"True, they are considered Muslims when it comes to certain rulings, ONLY TO MAKE THINGS EASY FOR US AND TO AVOID BLOOD-SHED."
So they're treated as Muslims ONLY in certain rulings of Islam, so they're not exactly Muslims according to you guys. Furthermore, he says it is done to lighten the burden off of the Shia (sounds like Taqiyyah) and to avoid spilling blood (which would have been Shia blood).
Because you're not mu'min. It is only haram to backbite mu'mins (some scholars seem to have allowed backbiting fasiqs even if they're Twelvers to be halal, at least in their public acts fisq, so that too). The condition for the hurma of gheeba is iman. Khomeini explained this well in Al-Makasib Al-Muharrama.
Al-Khoei here is talking about the reality of the situation, which is the fact that Sunnis in reality are kuffar. There is no switch, you need to look at things wholly.
Yes, not being a Twelver is worse than not praying, no issues with that. My point was that the laws of Islam are upon Sunnis, in this regard. Also by the way, when it comes to Hajj too (with a little more detail I believe).
Now, as for what Al-Khoei said is the point of these rulings, that is the reason for these rulings but not the means which the fuqaha use to get to deduce these rulings (which has been explained in the discussions above). The Imams may very well have told us to treat Sunnis as Muslims due the reasons Sayyed Al-Khoei has stated (although some other scholars may disagree with this).
Which is why I believe Allama Al-Majlisi says these rulings will change once the Imam (as) has returned, to which the hujjah will befall upon the Sunnis these time outwardly, and disbelief will result in out and out kufr both dhahir and batin because there will be no shubha anymore.
Are Qadiyanis Muslim as per al-Khoei?
I would assume not. Haven't seen him explictly say anything regarding them.
Why? They claim to believe in shahadatayn and Day of judgement. Which this criteria he must believe they are Muslims as well.
It may contradict the belief in Nubuwwah
In regards to contradicting the belief in Nubuwwah, there is a shia narration which states that denying mahdi (or was it any of 12 imam) is equal to rejecting Nabi shallallahu alayhi wasallam's nubuwwah. Anyone care to confirm if that's authentic?
In reality, there is no difference. The only difference is the Fiqh Laws and outward treatment differs. But in reality they are the same.