On the other hand, I'd like to conduct a study on the sorts of people who enjoy shows with villain protagonists and see how high they rate on the Dark Triad.

I would very much like to read the results of such a study! Including from participants who write and direct those shows. For example, I've heard (though have never watched) that Game of Thrones (massive following) portrayed gratuitous rape scenes. That's just one example. When I see films or shows where they are so graphic with rape, I always wonder if the men who direct them are trying to appeal to some men's darkest impulses? And I wonder if the directors get off while watching such scenes. I ran that idea by a couple of friends and they thought I was nuts! Hahahaha. Oh well!