If our planet is ever invaded by space aliens War of the Worlds style and they start rounding up humans like cattle, butchering us, force us to fighting for their amusement, and generally treat us with no sense of ethics or respect...many people will ask "what did we do to deserve this?"
...and the aliens will have a PowerPoint presentation set up, It'll have pie charts and shit, bars and graphs of all the species we made extinct for dumb fuck reasons. And videos of all the terrible fucking things we did to the other creatures on our planet as well as the horrible things we did to each other for no other reason than because we had the power to do horrible things, so we did. And the aliens will be like "eye for an eye, right?" As a species, we won't have a retort.