As far as I can tell, most aliens are a lot like Vikings. They're mainly interested in resources and occasionally, women. They don't operate with any sort of value system, and they're more than willing to sneak up on you. They're the type of assholes who will kill you while you're taking a shit or during the last five minutes of the X Factor results show. There's no moral compass in play, and if they can smite you while your back is turned, all the better. That's why you need to be willing to utilize anything around you as a weapon.