Orthodox Christianity and Islam–of the “everyone with different beliefs than us deserves to burn in hell” variety–is responsible for some of history’s greatest crimes. This is obvious. Just as obvious as the fact that racism–of the “everyone with a different ethnic background than us is subhuman” variety–is responsible for some of history’s greatest crimes.
For people who have trouble seeing this, though, Sam Harris did a pretty good job of laying out the reasoning behind this in his books, with citations from the Bible, Koran, and Christianity’s most influential theologians (Augustine, Aquinas, and Calvin were all for violent repression of dissent). No one ever dicusses this, though, it’s always about what a big meanie Sam Harris is for criticizing religion. Well, almost no one: Victor Reppert just put up a pretty good post on the subject. I thank him for it. Here’s his account of the reasoning:
1) Our beliefs are true, and others are false.
2) Whether you accept our beliefs or not determines whether you go to heaven or to hell.
3) The people who promulgate these other religions are putting other people’s souls in danger.
4) Even if we have to forcibly stop them from so, we can prevent them from leading other people on the road to hell.
5) Therefore, the use of force in the name of religion is justified
Vic claims this argument is incomplete, which is true, but the gaps are easy to fill. (2) can be taken as a premise, since historically it has been widely believed by Christians (and there’s support for it in the Bible, see John 3). (3) follows from (2) plus the empirically plausible premise that vocally advocating a belief tends to cause people to accept it. Similar situation with (4).
The only step that should cause much controversy is (5), because you need to add some moral assumtions to (1-4) to get (5). But what those moral assumptions are doesn’t matter much, most ethical views that take the consequences of our actions seriously will do the trick. Unless, under your ethical code, there’s something that can trump the eternal damnation of many, many souls, at that factor is present here, (5) follows.
One of Vic’s commenters suggested free will as a trump card. It’s an often used trump card in a lot of debates. But here it’s especially hard to see how free will could be relevant, because we’re talking about human actions, and humans do things to influence eachother’s behavior all the time without, presumably, messing with free will in unacceptable ways. Most Christians would not take seriously for a second the idea that police work or missionary work should be prohibited for fear of violating people’s free will.
Further reading: Augustine’s letter to Donatus provides a nice set of responses to common objections to this reasoning. For those who have access to academic journals, I recommend Craig Duncan’s paper “The Persecutor’s Wager,” which again responds to many objections, though oddly focuses on the specific ethical theory consequentialism, rather than talking about the implications of just taking consequences seriously.