Exactly. The most dangerous people are ALMOST ALWAYS in some narrow sense puritans: people who elevate a single principle above all others may do so and justify almost anything in its name.
The kinds of people who burned William Tyndale and Giordano Bruno at the stake are similar in this way to the kinds of people who justify racial purity and who condemn outright the wickedness of property rights.
The dangerous thing isn't religion, per se. It's the distillation of virtue into isolated principles with a universal application. Once you do that, you can justify all kinds of hatred. And those who oppose you seem simply to be an evil to be snuffed out.
The most dangerous people aren't those whom we would easily see as lacking virtue. The most dangerous people wear a mental hair shirt. They seem to be highly principled. And they will do all sorts of evil things in the name of their principles, which they and others misidentify as virtue.
Virtue is a compound. It is not an element.