Religious freedom: A key to other freedoms?

A friend writes to say that Paul Marshall, with whom I worked years ago, has published a book surveying religious freedom issues (Religious Freedom in the World, Rowman and Littlefield, 2007). I can't seem to find the book online, but here is an article summarizingmarshall's findings:

Religious freedom also correlates highly with other human rights, such as Freedom House’s civil-liberty index (.862) and political-liberties index (.822), and with Reporters without Borders press-freedom index (.804). Countries with good religious records also have comparatively little social conflict, remain democratic, and are unlikely to become failed states.

That, of course, make sense, because countries that discriminate on the basis of religion are likely to face high levels of unproductive conflict. And - as Marshall would be the first to say - freedom of religion always means freedom to disbelieve as well.