Rape Is OK When It's Sci-Fi

The phenomenon in (and mindset of consumers of) Hentai and other erotic works, in which introducing enough sci-fi or fantasy elements into scenes of non-consensual sex heavily reduces the perceived moral repugnancy of what is still essentially rape. The intention is that, when the circumstances surrounding the scene are sufficiently removed from reality, the viewer feels significantly less guilt for being entertained by it, since the scene as it plays out cannot possibly be reproduced in real life. (Obviously, your mileage will vary depending on your tolerance for such things.)

Common elements of this trope include:
 * Blue and Orange Morality, when the assaulter is a Starfish Alien with an entirely different set of morals from humans, and is by its very nature unable to comprehend why any other species would consider its actions wrong.
 * Brainwashing, usually through some sort of Applied Phlebotinum, to artificially induce pleasure in the victim, so that the assaulter can assert that “"It's Not Rape If You Enjoyed It"”.
 * Naughty Tentacles, which are so utterly outlandish by their very concept that they cross the line twice, reducing the gravity of an otherwise touchy subject.

It is entirely possible for authors to undershoot the mark if they are applying the trope intentionally. Too few fantastic elements, and the scene becomes realistic, and therefore not entertaining (except to actual potential rapists).

In any case, if you know anyone who enjoys some really fucked-up porn, and yet is otherwise well-adjusted in real life, this trope is probably in effect.

No examples here, please.