It is perhaps the core tenet of liberalism that people can believe something strongly while not asking others to believe as they do. This is what tolerance means -- it means I think what I think, while accepting, even embracing, your right to believe something else. In practice, though, this is hard for most people to do. The Pew Research Center has been asking people for years, in differently worded questions, if people of other faiths can go to heaven, and no matter how they ask the question a majority of Americans answer yes.
One very plausible explanation is that Americans just want good things to come to good people, regardless of their faith. As Alan Segal, a professor of religion at Barnard College told me: “We are a multicultural society, and people expect this American life to continue the same way in heaven.” He explained that in our society, we meet so many good people of different faiths that it’s hard for us to imagine God letting them go to hell. In fact, in the most recent survey, Pew asked people what they thought determined whether a person would achieve eternal life. Nearly as many Christians said you could achieve eternal life by just being a good person as said that you had to believe in Jesus.So the fact the American Christians are constantly exposed to Jews, atheists, Hindus, Indian traditionalists, and the like undermines their Christian faith -- because it is, after all, one of the core beliefs of Christianity that no one can be saved except by faith in Jesus.
Religious fanatics of every stripe have always understood this, which is why they have tried so hard to control what their people are exposed to. By some combination of separation of themselves from others (Catholic schools, Fundamentalist Mormon compounds) and control of the social discourse, they want to limit their people's knowledge of other beliefs. It is easier to believe something when everyone you know also believes it, and even easier if you can believe that there is something wrong with everyone who doesn't believe it. A tolerant society will be one with much less fundamentalism and much more wishy-washy belief.
This conflict has been most open in America lately in the struggle over gay marriage. Various religious figures (including Rick Warren) have argued that public tolerance of homosexuality undermines their religious freedom. The forces of tolerance say that this is silly, that they aren't asking fundamentalists to marry gays in their own churches. But I understand what they are saying. What is socially acceptable does influence what people believe. (Thus the great battle by liberals to make racism socially unacceptable.) People who are surrounded by married gay couples will be much less likely to condemn homosexuality. Sure, the strongest believers will only be made more certain by social opprobrium, but most people are not like that. Most people go with the flow.
I, of course, celebrate this. The more wishy-washyness the better, as far as I am concerned. But I do understand that making the world more to my liking will make it less to the liking of millions of believers.