After living to middle-age in the West, I'm sure all three women, no matter how mcuh a gaggle of old biddies they may be, have done many things which, going by the decrees of Muhammad, would "justify" doing exactly that.
Actually, just by not being Muslim, and therefore of the Dar al-Harb, should they refuse to accept dhimmi status and pay Islam its "protection" money killing them would be considered no more a crime than swatting a fly.