but why not?
If copyright licenses on works could be had for cheap, everyone benefits. Sure, disney benefits a lot, since they can make use of the work more efficienty in large productions, but the result of _their_ work could also be had for cheap (such as someone else taking the disney movie and remixing it for low cost).
> Shouldn't I be able to stop them?
no you shouldn't, if said neo-nazi propaganda wasn't illegal to begin with.
As for what percentage of the derived-work revenue needs to be paid to you, just let the deriver pick something that they think is fair. It'll be part of the metadata on that work so everybody can see how much of what's being paid is being passed along.
Then we create a culture of amplifying works that are fair to their dependencies. As for those that are doing and bare minimum, we name and shame (and sabotage?).
Surely all use cases can't be the same amount. If I write a song and Disney uses it in a Marvel movie presumably, I should be paid more than if some local high school kid uses a 10 second sample of the song during their garage bands production.
What if a bunch of neo-nazis want to use my song in their propaganda video? Shouldn't I be able to stop them? Their use would be a detriment to not only the commercial value of my work but potentially to myself as well.