I think I know what he's getting at. -nods-
If I were a Xeno, would I kill? Yes, just to secure the life of my Hive. I would capture my prey, take it to the Hive and hang it up on the wall in a chamber where the hatchlings would take hold of him. Now, if my prey is a very hostile one, I would have no choice but to kill it, for there is no point on waisting my life just to capture it and have have the younglings bore a new family member.
Really, how I think of Xeno, after awhile of listening and watching the movies, yeah, they are a savage race, but how would they live if they are not able to multiply, by killing all the hosts? So here, they would rather capture their hosts alive to increase there number, but if the host is too hostile, like a Yautja, you have no choice but to take it down. Now a human on the other hand, they can be stubborn. The Xenos, they could surprise them and take 'em to their hive, or they are just like the yautja, you have to kill them to keep your numbers from dwindeling.
That is what I think.
Wars are the Dread of Mothers