The takeaway is that they are human predators. Just beware they exist, are prevalent, and you won't easily fall victim to them.
Also an insightful comment: "The sad part of this sad letter is that she gets off on it... She has NO EMPATHY.. It boosts her friggen ego.."
Definitely true. It's really difficult for so many to understand. The no empathy part doesn't mean there's a little bit there, it means none, and the person experiences joy and satisfaction through malignant avenues.
It's not too difficult to understand if you simply accept there are people opposite to the ideals of Christianity, where every Christian virtue is inverted. You have to stop trying to see the good in everyone and stop with the nonsense about us all being God's children.