At one point in life I'd have agreed with you. Now I can't agree with this at all. Usually the West wants very specific kinds of freedom; the kinds which are useful for social control. The first amendment may remain in the US as a sort of residual idea from classical liberalism, but it seems not too many people actually want this.
I'm not sure the first amendment was ever really popular - Nazi's marching down a Jewish neighborhood, hippies burning the American flag, John Adams defending British soldiers involved in the Boston Massacre - freedom is often very unpopular. Just because something is unpopular doesn't mean it's not sacred.
Yes, I get that's the point, but it's consistent with my original point: the right to be disagreeable, whether an outsider or not, is an important freedom that's valued in the U.S., regardless of whether it's a net socioeconomic benefit or loss.
You're missing one of the major points: freedom. The issue is not just weighing the utilitarian pros/cons of allowing diversity of thought. In the U.S. (and generally the west), the ability to think and do what you want is valued as an important individual right that each person is entitled to, regardless of whether it's good or bad for society as whole.