If you read the translated doujin it's extremely obvious that the author made that doujin as a way to lash out at the ending. It's not just some f**cked up fanart but something created out of ill intent and bitterness. Which makes it worse.
All of us hate the ending, but I doubt very many people here would go to that length to protest. And I agree that the NS fandom shouldnt be generalized based on one rotten apple.
So you read the doujin?
On a scale on 1-10? How kittened up is it?
(Yeah, I'm pretty sure I know the answer to that)
It has adultery & rape.... It goes over the scale.

Found them both her and her brother
Now give me my prize 

HAHAHAHAHAHAHAAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA