I don't buy into the whole no killing women or civs thing, killing men civ or otherwise equally bothers me, now granted i've played plenty of games and am happy to slaughter when given no other choice - those poor defias, how many of you have I slaughered? - but if I can play through a game by stealthing and or non-leathal elimination I will much prefer it, and infact will ocasionally feel guilty killing when other routes were possible. i'm even open, heck would encourge, temporary non-leathal take downs.
No One Lives Forever 2 was a great example of this, you had a tranq dart for your utility gun that would knock enemies out for something like 20 minutes, but after they awoke they'd run off and sound alarms and what not, which made co-op rather fun and challenging on harder difficulties. Me and my friends would agree to use the tranq - might also have been a tazer - because you had to get through missions faster and with better precision.