What kind of small, hateful person says "women, children, and other civilians" instead of "people" or "civilians"? How fucked do you have to be to value the life of one person more than another because of their sex or adulthood?
This isn't pretty, but human life isn't equally valuable and there are nearly infinite ways this can be quantified. First, it's subjective, and second, only a handful of reasons a rational person would agree with. Some examples:
Children generally have more time in front of them and therefore are being robbed of more when killed. If you had to choose between the death of a five year old or a 90 year old, which would you be inclined to choose?
If you believe in justice/punishment/retribution/etc., older people are more likely to have committed acts in their life that are worthy of punishment, while younger people are less likely. Obviously that doesn't necessarily mean they deserve to die or that there's actually a connection between their sins and their death, but again if you had to choose between an aid worker and a serial killer being killed, which would you choose?
If the Earth were about to be hit by an extinction event and only 10000 people could be saved via sci-fi-method-of-your-choice, would you select people at random or choose the best-of-the-best with respect to the successful continuity of the species?
If someone points a gun at your head and says, "I'm going to kill you," you are legally justified in killing them in self defense, which indicates at that moment your life is more valuable than the gunman's. Were it not, you'd be expected to simply run away, try to talk them out of it, or use other non-lethal means to stop them.