I guess for me, as a person who gravitates to storytelling and writing, putting restrictions on what kind of stories are allowed is something I don't like.
The comment resonates, but there's a continuum of fairness. Gotta look at it from the other side of the coin.
If you write something that goes viral (let's call it the Harry Potter effect), and then someone else comes along and starts writing related stories using your characters and settings, that
also goes viral -- and they make gobs of money from it and completely ignore you as the creator (financially and otherwise)... How are you going to feel?
The core problem is that you can't predict whether something is going to be hideously popular before other people see it. You might write something that you think is stupid, but that the rest of the world thinks is the greatest thing ever. And in this day and age, once it's out there, it can't be stopped. And you can't predict how whoever appropriated your characters and settings is going to handle things.
Now imagine this happening with something that takes the characters you painstakingly created and paints them in a light that is entirely opposed to your beliefs; then things get
truly ugly.
In legal terms, the answer is already defined: you created it, you own it. Period. The exceptions are narrow enough that they may as well not exist for the purposes of this discussion.
In moral/ethical terms, opinions vary (had a debate on this with someone much earlier in this thread if you want to see a very vehement alternate viewpoint). I don't see a good solution. When have you copied too much? There's obviously a line there -- but who defines it, and where is it?
I don't know what the solution to the conundrum is, and I don't know a better answer than the current legal one. If I'm remembering correctly, my last debate on this topic started because I mentioned that I wouldn't mind seeing an adjustment in the definition of "fair use". But I'm not nearly smart enough to figure out an equitable solution that protects the original author.
(on an unrelated note, I really wish the post editor wouldn't keep adding incorrect and useless size tags. I always forget to switch to text mode, and end up having to go back and remove them all...)