We cannot afford the luxury known as conscience. The enemy we are up against certainly doesn't have one, so we are obliged to be absolutely rational. Cruel, if you like. People of good will, tolerant, liberal, whatever term you care to use, have always labored under a disadvantage. Those in power, those who want to hold on to power whatever the cost, have one ultimate recourse. If all else fails, they are prepared to kill. This is not available to pacifists.