I think there's a lot of good lessons to be had in here. We could talk about the fact that human history seems to trend towards a better and more kind world, which I think is true--and which I also think is a good lesson a lot of doomsayers could take from studying history.

Or we could speculate about the societal conditions that made it normal for women to poison their husbands. I'm... well, I'm sure that there were some husbands in the 600 victims who we would agree didn't deserve death. But I suspect if we had a chance to interview the women who did it we'd wonder why a lot of them didn't poison their husbands sooner. That seems like a good lesson: society shouldn't trap women in abusive marriages and then be shocked when they go "Goodbye, Earl."

To be honest though the lesson that pops most readily to mind is that if you're a freelancer the quality of your referrals matters a lot for your well-being.