From 9-11 to this day, callers to my syndicated radio show have asked: "Is Islam a religion of violence?"
And since 9-11, I have given the same response: "I don't judge religions; I judge practitioners."
It is easy to dismiss this response as a politically correct cop-out, but there are good reasons for this response.
First, in medieval, or even parts of early modern, Europe, many people would have asked, "Is Christianity a religion of violence?" And 2,000-3,000 years ago, people might have asked, "Is Judaism a religion of violence?"
Second, the question is often impossible to answer because religions are almost never unified in their values (and often not even in their theology). For example, most evangelical Christians have almost no values in common with fellow Christians of the National Council of Churches (NCC). Conservative Protestant Christians share far more values with traditional Catholics, Orthodox Jews and Mormons than with fellow Protestant Christians of the NCC. And liberal Jews (not only secular ones, but many Conservative and most Reform Jews) share more values with liberal Christians and liberal atheists than with Orthodox Jews. So when assessing Christianity or Judaism, which Christianity and which Judaism are we assessing?
Third, when groups are violent, how much of their violence is directly caused by their religion -- or by their irreligion? Alongside Hitler (who believed in no religion), Stalin and Mao were history's greatest mass murderers, and they were atheists. Could one have asked, "Is atheism a violent ideology?" As for religious evildoers, did European Christians who supported the Nazis do so because of, or despite, their religion?
Fourth, even when a group does attribute its violence to its religion, as in the case of Muslim terrorists, does that mean the religion itself preaches violence?
Many people would offer a fifth reason not to judge religions -- that doing so is inherently biased, even bigoted, and outsiders have no right to judge others' religions.
But that objection to judging a religion is invalid.