> Violence is also a constant presence in world history

Actually, it's not constant. It's decreasing.

Check for Steven Pinker on violence. The further into the past you look, the more violence you find —of any kind. Go back to the period where we lived as hunter-gatherers, in Harmony with Nature, and suddenly nearly 2 men in 3 die at the hand of fellow humans.

So, while History does show an everlasting presence of violence, it also shows that this is not hopeless: slowly, steadily, we are making progress. I'd keep an eye out, though: we're not there yet, and each death still is one death too much.