Fact of the matter is that it worked in the past... and since human nature hasn’t changed one wit since then, it’ll work now.
Whether that gets your panties in a wad doesn’t change that fact.
(Or in other words, terrorists can’t be very good terrorists if they’re too busy being terrorized.)
Just because it works, doesn’t mean it’s right. Look, I hate Islamic terrorists, and I’m not at all fond of Islam in general, radical or otherwise, but surely there should be some limits as to what is allowed in war? Sherman (and especially the camp followers that he allowed to hang around) hurt a heck of a lot of more people than just enemy combatants. Do we really want to see non-terrorist Middle Easterners attacked and their land destroyed, just so long as actual terrorists are hurt too? What do you really think the end result of that would be? A whole lot more terrorists seeking revenge for their mothers’ deaths and sisters’ rapes coupled with a never-ending occupation, I would imagine.