Things that overcome and eat other things stay alive to reproduce and propagate. Those that can't, cease to exist. This very fundamental aspect of nature implies that there will always exist some selection bias towards aggressive predatory behavior among the most successful products of evolution. It's interesting to consider that the 'morality' of herbivore vs carnivore is an entirely human conception. Go back far enough and humans and grass share a common ancestor. We just evolved in different directions.
In any case the development of higher intelligence enables us to overcome and suppress or evolutionary instincts. But I imagine these instincts will always be a part of us. I see no reasonable way a highly advanced species could have ever evolved without them. And while the media and other players sensationalize violence, the reality is we live in what is likely the single most peaceful era of civilization - ever.
Try to imagine that in WW2 around 70 million people died from a world population of 2.3 billion. That's more than 3% of the entire world's population killed. Scaled up to present day population that would be more than 231,000,000 killed. Since we suck at understanding such huge numbers. Let's convert that in 9/11s. That would be more than 77,000 9/11 scale events. In other words imagine we had a 9/11 scale event every single day for 211 years. That's how many people died in WW2. Today we in the developed western world freak out about 60 people dying, and a single 9/11 is a world shaking event. And go back to things like the Mongol invasions - they were on the order of 300% more deadly the world's population than WW2 was. One can only imagine the actions within prehistory among isolated populations. Perspective.