You're forgetting that lions don't just kill their prey; they kill lions from other prides. Male lions will frequenly go out of their ways to confront other prides and slaughter the cubs. To bring it closer to home, chimpanzees exhibit the most brutal behavior not toward other animals, but toward each other. It may be a survival mechanism, but my assertion is that the very act of satisfying an instinct generates what we call enjoyment.
If anything, civilization brings it out in us more. Without the need for survival as an outlet, we're stuck with these instincts and nowhere to direct them. So we shoot each other.