You may think the world is going downhill, however, humans have become less violent over the centuries. Just because you’re aware of more recent atrocities, doesn’t mean worse things didn’t happen in the past. If you account for the number of people alive, the worst atrocity is An Lushan – a civil war in China during the Tang dynasty that killed about 2/3′s of China’s population = about 1/6 of the worlds population. And I bet you never even heard of it – like myself.
Another interesting data point, we no longer go to hangings/executions for entertainment, nor do light animals on fire for pleasurable viewing. Times have changed.