http://en.wikipedia.org/wiki/Sunni_fatwas_on_Shi%27as
like this:
Sunni fatwas on Shi'as show the how the Sunni view of Shi'a is documented in legal rulings.
The renowned al-Azhar Theological school in Egypt, one of the main centers of Sunni scholarship in the world hade a ten year long exchange with a Shia scholar. After a long period of discussions, they announced the following on July 6, 1959:
"The Shi'a is a school of thought that is religiously correct to follow in worship as are other Sunni schools of thought."
Today, both Shi'a and Sunni students graduate and study at the Al-Azhar university.
This statement have been received with a variaty of responsed, most hostile being the ones from the Salafis.
1. Ibn Hazm — "Shia are not even Muslims", when christians debating him brought a Shia book as reference. See: al-Millal wa al-Nahl الفصل في الملل والنحل 2/213
2. Ibn Taymiya
3. Ibn Khaldoun — "astray people", "shia are the source of all deviant groups in Islam history".
4. Nizam al-Mulk in his Siyasatnama, chap 41, where he fully attacks The Rafidhun.
Interestingly, the latter author was assassinated when he converted to Shi'ism after a Sunni-Shi'a debate held by the orders of Malek-Shah, who also followed the same fate. (source: see Mughatil ibn Bakri)