I think it opens the very front door to witchcraft, sorcery, and the like.
Look at Rev. 21:8 But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death.
Would anyone here say God would approve of watching activities of people in any of those categories of wrong-doing?
Maybe a list of scriptures forbidding more than a casual glance of things that lure people to sin would be an interesting addition to your topic. There's plenty in the NT alone. Maybe even letting our eyes wander at all from dead center, looking to right or left is too much for our good.
I can apply that to Harry Potter because my wife and I decided to watch one of our grand's DVDs of the series, only to observe and try to explain why they are not good to watch. I know what it's about, don't have to go look up reviews for my opinion. We succeeded. Now, when something comes over TV about Potter they instantly react, telling how bad it is, that all the characters in Potter will go to hell. I'm not sure they understand those are just actors becasue of the very realness of the scenes.
Be fishers of men