Her argument isn't "lol birds are great" or whatever it is you said. If your Watcher paid any attention to the world around him he would have seen the immense suffering caused by the Hollowborn and the terrible effect it is having on all of society. For some characters, it's not enough that the souls would be reborn if they were returned to the cycle, that's an academic truth maybe, but it doesn't have the sense of justice that returning the souls to their rightful vessels has. Remember, side with Berath, and healthy births will start again, but thousands of parents of Hollowborn already living will never see their children look them in the eye, they will care for soulless husks until they die. For an academic assurance of security, some would pay that price, but it is hardly the stupid decision you paint it as. It is a valid option.