What exactly does “fanart” (no matter how distasteful and controversial) change?
Let people generate whatever fictional character they want.
Why should Disney care?
To which you might say “because people care”, so:
Why should people care?
Back when I was a spud I used futuristic text-to-speech synthesis to make my computer say “Eye am Bill Gaytes my farts go FERT FERT FERT” - Should Bill Gates be offended? What about the people who like him? What about the Intel processor I used to create it? Or the company behind the TTS software? Would anyone think they’re involved and endorsed it? I guess the real question is: are we catering the world to people who can’t make that distinction?
The way advertisement works is that it's brain hacking - it's just associations. Over time your brain associates a brand with a product or products, and then simply by having this association in your brain you're more likely to buy the product.
This also works for negative advertisement.
Think about it. Suppose you did see mickey mouse saluting Hitler, or maybe you saw mickey mouse stick a jar up his little rat ass.
When you see mickey mouse, undoubtedly, even if just for a second, your mind will think about what you saw before. You might discount it immediately, but the damage is done. You still feel that emotion, even if only for a split second, and you have been influenced by it.