A bit misleading. I'd say that the Shia' consider Ali as the next prophet, but not as the 'rightful prophet'. They still consider Muhammad as a prophet. Otherwise, Formless did a good explanation of things.
With a religion the size of Islam, it is really hard to say who believes in what. I've met plenty of Sunnis who believe Shia' should be killed, and plenty who get along just fine, hug each other. I'd say most Sunnis view Christians and Jews as more closely related than they'd view Shia'. Intolerant Sunnis would still get along with a Christian, but very rarely with a Shia'. One is considered misled, the other is considered a traitor.
There are many people, like myself, who refuse to take sides and neither identify as Sunni nor Shia'. It's arguably forbidden to identify as either sect (Quran 6:159
I wouldn't say the Shia' are 'intolerant'. Rather look at the political angle. They believed that Ali was... treated unjustly by certain factions, namely the Abu Bakr group. They have a strong hatred for those who supported Abu Bakr's political objectives. But with the degree of influence that Abu Bakr had on Islamic history, that's a lot of people to resent.
Oh, I didn't mean this as any sizing up of your argument specifically, with regard to those persons from the first hundred or two hundred years of Islam. Ali and Hussein are central to Shi'ism, that's for sure, I mean they are the defining heroes of the movement. I was trying to characterize a tendency to bring key persons and struggles of those years close into talk about modern-day, present-day politics, it's a tendency I've noticed with muslim friends of mine here in Europe. I've also seen it pointed out a few times by researchers and historians around here (in Scandinavia) who have been working for decades in middle eastern history and politics.
I can see the merit of digging into the roots to unravel something, when one is bringing out something that's been happening in history sometimes that's what you have to do - look at what happened early on, discuss it and reassess it. My point was that there's a sort of unconscious difference to the west here. Most people in the modern west are not that heavily concerned with history in this way, not even the early centuries of our own religious and cultural core traditions. You won't often hear a Frenchman, a Brit or even less an American arguing passionately about the merits of Pericles, Cicero, Augustine or Alexander the Great, or using them directly, off the cuff, for comparisons with modern politicians, constitutions, writers or religious leaders. I think there's much more of an attitude of "yeah, okay that's history" here - even if Alexander the Great is admirable and influential, within antiquity, he isn't really a figure who belongs in *our* modern world - the world we know personally in some sense - his campaigns and opening up of the eastern world happened a long, long time ago...although they can become the stuff of movies! The same with Augustine, Bede the Venerable or even most of the apostles of Christ - they are historical figures from a long time ago, but not everyday, immediate points of orientation to us.
I'm an Islamic history fan, even minored in it in college, and I read a bunch of historical theses as a hobby
It's hard to explain this in a short post, but I'll try. Islamic dogma is based on two things - the Quran itself, and historical narrations and judgements in the form of "Hadiths". The Quran itself is straightforward. No Muslim would speak against the Quran. It's just about interpreting verses differently. For example, the verse 24:31
either means that Muslim women should wear a shirt (cover their chests), wear a long hijab (wrap their headcovers over their chests), or wear a long veil (wrap their facecovers over their chests). Different cultures translate that verse differently. But this is up to the theologists and Arabic language experts, nothing to do with your armchair Islamic historian.
A Hadith is a chain of oral narrations, something in the form of "Abu said that Malik said that Ilyas said that Jabar said that Muhammad said so-and-so is evil". Normally they would be a few of these from different chains in order to prove that Muhammad really said something.
Now the fun part is that if you can prove that Malik was not a reliable person, everything that includes him as a narrator falls apart.
There are tens of thousands of Hadith out there. So being able to hold the power to mix-and-match what you want to believe falls on proving the credibility of certain historical figures.
Let's take an example more relevant to modern times. It's said that leaving Islam (apostasy) is punishable by death. This is supported by several Hadiths in Muhammad's time saying that Abu Bakr, Umar, Khalid killed people who apostated.
The ruler of many countries do not want to actually kill apostates, because it's a hell of a legal mess, hurts foreign relations, kills important members of society, etc. But opposition radical Islamic parties will often support it... it's easier to campaign to change to a controversial law than it is to improve the economy.
For those who debate the law, they can say the following:
1. It was never explicitly in the Quran that apostasy is punishable by death. There's the base ruling that "anything which is not explicitly forbidden is permissible", meaning that it's permissible to let people go for apostasy and permissible to behead them for apostasy.
2. Various interpretations of the Hadith that support that ruling - mainly saying that it was 'tax evaders get beheaded', not 'apostates get beheaded', because Muslims during the era were given some tax cuts.
3. Some historical evidence of people who have apostated and were released. Since there is no evidence of this, it lends more credibility to the anti-apostasy group.
4. Removing the credibility of any Hadith that supports this. This can be done by discrediting Abu Bakr's inner circle. This is also why the Shia' is considered a different religion, even though they hold only political differences at heart.
While Point 1 above is a matter of theology, Point 2, 3, 4 of the above require some very strong historical knowledge to support. A non-Muslim with considerable Islamic history knowledge can argue what the religion says, even if he has never read the Quran.
And because of the 'inverse pyramid' system of the Hadith narration chains, those who know about the early Muslims have the most power to manipulate this system. Arguably, those who are knowledgeable about the later Muslims, including the Abbasid (golden age) era of Islam are not able to use this knowledge for political purposes. You can study the most recent 1000 years on Islam and it won't be as influential as the first 30 years.