The Klan are/were Christians, they were simply denounced by other Christians in more contemporary times for being extremists, but they were very active nationally here in the states in the 1800s and first half of the 20th Century. They're just a fringe now. Similar to 'moderate' Muslims who denounce the more orthodox or extreme/jihadists. I think the primary difference between Western Christians and Muslims is that Christianity experienced The Renaissance, The Reformation, and The Enlightenment movements where more secular views were mixed into the public consciousness and the interpretation of the doctrine in various denominations. Also the Catholic Orthodoxy losing a stranglehold on the interpretation of doctrine for the masses and the splintering of Christendom. We still see that today with the softening on positions regarding homosexuality and science in various denominations where others are more opposed citing doctrine. The Religious views adapt to the society, for the most part, rather than the opposite. Some denominations are far more orthodox and repressive, rejecting modern influences and sticking to a very strict and literal interpretation of the Bible (like still having women cover their heads with scarves or bandanas when reading the Bible with their children or praying, for an odd example of this), whereas other denominations stick primarily to using a very liberal interpretation of the New Testament/Jesus and essentially truncating the Old Testament from the narrative, save for a few passages, due to the horrible stories depicted in the text. If Christians stuck to a more literal interpretation of the Bible and adhered to the passages which state that Yahweh/Jehovah is unchanging and his laws are eternal, as well as Jesus stating that he didn't come to do away with the law but to fulfill it, Western Society could possibly also be an assemblage of theocracies still living under varying degrees of enforcement of Levitical Law.
Extremists always scream with the loudest voices because they are usually in the minority. I don't know the exact percentage of the billion+ Muslims who believe in violence to all infidels, but it's not a majority. Most of these people live meager lives and just want to be left alone to practice their faith in peace. Unfortunately their religion is be using to perform barbaric acts of violence.
As far as the comparison to extreme Christians to extreme Muslims, I can't remember the last time extreme Christians killed thousands of people, beheaded innocent people, took over sections of a country with violence or kept women from voting, driving, etc. I know the most recent large movement was the IRA. But I believe that has all but stopped. Then there was the Crusades and Inquisition centuries ago. If there has been anything large scale more recently I'd be curious to know about it.
Christians make up several sects like Catholics, Protestants, Methodists, Greek Orthodox, Evangelicals, Mormons, Lutherans, Baptists, Presbyterians, etc. There are some fringe sects and people but they hardly represent most mainstream Christians.
I actually think Affleck doesn't understand Harris's point well enough. He was a bit too combative in regard to religious criticism. But yes, the whole thing is very relevant.
He also inadvertently proved Harris' point at the beginning. Harris made perfectly reasonable criticisms regarding Islamic beliefs and said that people should be free to criticize without being labeled as racist, and Affleck, who I think wasn't even listening, essentially just started screaming "you're racist!". I guess that's why Affleck is a movie star and not a scholar.
I posted a similar opinion on another site. I think Affleck's problem was he got too angry. I agreed with what he was trying to say. He just couldn't say it without getting furious. It's true: hundreds of millions of Muslims are peaceful people who would never condone the actions of some of the more extreme. Just because some countries with lots of Muslims who are at war or just recently at war hold stupid opinions, does not mean they represent the other hundreds of millions of Muslims.
Also, did Islam make them like that or are they like that for other reasons and Islam is used as an excuse?
Lemme give you another example: Mormonism is fraught with self-righteous judgementalism. It is infuriating. Our religion actually teaches us, officially, to do the exact opposite. That doesn't stop tons of Mormons from persecuting homosexuals and ostracizing them.
Basically, to argue against Harris, because I'm clearly better at it than Affleck:
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Would you look at that: Muslims are the least militaristically violent group.
Second, but a distant second are your Mormons. I'm actually shocked. Mormons supported Bush, in general.
Also, if we REALLY REALLY want to argue against Harris' position, Gallop conducted a ridiculously awesome poll and in the poll, they conclude that the radicals comprise about 7% of their group. That's quite a bit and considerably more than probably any other religion in the world, imo.
A majority did not support the 9-11 attacks, which is important. That's a majority: hundreds of millions of Muslims.
I think that last link, everyone should read. It shows you that, yes, Muslims are pretty damn violent compared to other religious groups. But it also shows you that they are not all horrible violent beasts.
Edit - Also, if Ben would have done just about 2 minutes of research before going onto that show, he would have been able to hand Harris' ass to him. Instead, he just got b*tchy.