No, I quite agree with the intellectual honesty, especially about not stealing copyright contracts.
So, if we're talking about intellectual honesty; there really is no possible conflict on that issue alone.
As far as copyright law goes; violating copyright is far more bother than it is worth, no matter if someone gets away with it or not- it is infinitely far easier to go with making up one's own story inside another person's universe and including a disclaimer than to violate copyright as it turns out.
As for the claims of rank; that's never going to work at all in your favor, but the situation is with intellectual honesty is completely agreed with immediately.
However, if you fear them coming after you, you pretty much make sure they will as it turns out.
Paid for writing fanfiction; basically that alone violates copyright law, not to mention the even more binding, and rightly so, matter of intellectual honesty.
The only way anyone would be able to be paid for a fanfiction is with a written contract with the copyright holder; anything else is highly illegal.