via Rightwingsparkle (who has a different take on Alan Moore here.)

We have to put our hands up and admit to our complicity in the sexual problems we have. As for incest, yes, in real life, incest is very, very, very seldom an idyllic thing. It's much more often a monstrous thing that destroys people's lives. However, we're not talking about real life. We are talking about the human sexual imagination. Sigmund Freud, frankly, I've not got a great deal of time for, because I think he was a child-fixated cokehead, to be perfectly honest. But his is still the prevalent paradigm in our attitude to sexuality. And Freud said that all sexual desire was sublimated incest. I don't agree with that for a moment, but it does suggest that incest is one of the big players in the theater of our desires. So that has to be referred to.

We felt we had to explore even the problematic areas of pornography, because they're a big part of pornography. We didn't want to be accused of turning out something arty that claims to be pornography but isn't. We felt that if we were going to do this thing, we were going to have to do it properly. We wanted it to be as pornographic as possible, and as artistic as possible. We wanted it to be a pornography that would include even the more extreme pornographies.