I call BS on most of the stories, as I'd like to believe the majority have some sort of conscience or heart. I haven't had a telemarketer call me in a very long time, and that may be because I ask them to remove me from their contact list when they call.
Being a d!ck to them only satisfies peoples inherent need to put others down. It's a coping mechanism, and taking it out on a target that you'll never see or hear from again makes it that much easier to accomplish.
I PC proper grammar...just a warning