"Simply killing her would not have been sufficient?" He's been desperate, fighting what seemed at the time a losing battle against a much more powerful opponent, and he's not entirely sure that he, or at least his side, as he'd not been the commander of the Alliance forces, just of his own Dixingren contingent, wouldn't have taken advantage of such a tool had it been at their disposal. And that despite having seen the horrors that the Rebel chieftain inflicted on not only his foes, but often his own people.