The most recent episode of This American Life (http://www.thisamericanlife.org/radio-archives/episode/545/i...) has Jezebel writer Lindy West reach out and talk to one of her trolls who created a page celebrating her father's death and claiming she was a disappointment to him. He sent her an apology after realizing there was an actual person on the other end of his trolling and they actually have a remarkably civil conversation about the incident. It's highly worth listening to.
This phenomenon can be found all over the place. Follow some of the cycling hate on twitter some time. People fantasizing about literally killing people with their cars. Why? Because they lost 12 seconds on their 30 minute commute?
It's a weird disconnection. The 'targets' are moms, dads, sisters, brothers, friends... people. I just don't get it. Why are some people so lacking in empathy?