There are various general topic tags like zombies, vampires, sex, fight, technology or revenge. Those serve primarily for either tagging identification questions or general questions about the depiction of those topics in movies. However, I don't see much use in creating a tag for each and every single totally generic topic a movie could be about. This is simply a tag granularity that does not fit to the scope of this site, this is not Everything.SE, it's Movies.SE and I'm not sure we want tags for e.g. cars, refridgerators or nazis simply because those things can be depicted in movies.
For identification questions we already have genre tags as further specification and I can't see people here looking for identification questions specifically about revenge or zombies. I see that even on our site there can be very well interesting and good questions about sex or vampires, specifically about their depiction and treatment inside movies and TV, but those also fit equally well into other movie-related tag categories, like reception, analysis, first-appearance or movie-rating.
This problem has been adressed a very long time ago where the respective tags got removed and in a more specific, yet unresolved, question about the revenge tag in particular. It has also been adressed in a very related question about the aliens tag (though, there the main problem was that there was also the specific movie-meaning of the tag).
But in light of the bigger recent tag cleanup proposal, that I don't completely agree with in its entirety, I'd still make an effort for drawing a clear line somewhere, and general non-movie-related tags is exactly that line we shouldn't cross. Allowing tags for each and every general topic depicted in movies but not directly related to movies would just open the tagging system to an arbitrary explosion of unhandlable tags and divert from the core topic of our sites. I'd thus hereby generally propose the removal and prohibition of such overly generic topic tags unrelated to movies and TV. I already adressed that at the end of my broader answer to the tag cleanup question, which seemed to have met some agreement, but would propose this here in a more canonical and condensed form.