I think you've already mixed several things- ff writers never claim that they invented characters and usually copyringht prevent them from being published without permission. In USA and Western Europe, at least- Russians have very lax copyright and when it comes to fantasy lots of writers actively encourage fans to help them and come with own stories. I must say that I like this attitude- the original will always be the original and there's nothing bad in making fictional universe more diverse. 

Remember that our whole culture is one great fanwork- you may devote your life to trace things based on Bible, Greek Mythology or Arthurian Legends and that won't be enough.

You have to let your work fly and let the reader put their own end caps on things.

On the other hand lots of people say that Nabokov supported paedophiles- granted, mostly those who were prejudiced from the start, but still.

I must say that I often have the problem with historical fiction, mainly with the way most of the authors handle values dissonance- and I don't day about things like 300 that just take some fancy tokens from the past but so called "historical fiction". No matter time and culture, the protagonist will always have morals strangely resembling those preached by liberal upper middle class from USA- and I have an impression that lots of them either
a) didn't do research
b) did, but was afraid that the audience will react like those amazon reviewers who complained that "Kristin Lavransdattir" would be a better book had the heroes not thinking that much about religion.

I know it's risky topic that requires a lots of skill to make a protagonist likeable in spite of having different morals than reader, but it's possible. I understand that Melanie Wilkens wasn't abolitionist and that Mammy considered herself a better caste than field slaves. Petronius of Quo Vadis while being considered by his slaves as exceptionally patient and understanding man didn't hesitate to order corporal punishment when one of them didn't obey him on spot. Heroines of Lisa See couldn't be more different from modern Western women, yet they are interesting characters whose characteristic perfectly fit their time and background.

I don't say that character can't have some modern morals- Sometimes skilled writer can sneak them by presenting it as an extraordinary- like Judge Dee who gave shelter to rape victim and later married her to keep silent bad tongues (on the other hand he wasn't above using tortures while serving justice).

On the other side of the spectrum we have that guy from Patriot, pure as freshly washed clothes who see like a transplant from XXI century.