Well, this is a good point. I bet one thing we've never seen in a film that wasn't rated at least NC-17 is an ERECT penis.
Like, you can slip one into an R movie as long as it's flaccid. But once that thing gets excited, whoah!, look out MPAA!!!
Exactly. The line between art and eroticism can be blurry with regards to depiction of the female form because the state of sexual readiness is not as evident (unless we get all Larry Flynt) as it is in the male.
With men, it is cut and dry: Erect phallus = eroticism. Non-erect phallus = not eroticism.
The objectification of the female form is not restricted to strait men. We need only browse briefly though any fashion magazine like "Vogue" to see a sensual, semi-erotic presentation of the female form. Thus, objectification of the female form is driven as much by women as men.
Seeing full fronting nudity of men in film is simply shocking. There are several reasons, with homophobia taking a back to seat to most of them:
1. Seeing full frontal nudity in men is rare and it pops off the screen when we see it simply because it is rare.
2. Parents. When adults have a child, their view of the world can be fundamentally altered where they are highly sensitized to providing a safe and wholesome world for their children to live in. Parents with pre-pubescent children commonly don't like adult nudity in this world as they want to control how and when their children are introduced and exposed to strictly adult themes, especially sex.
3. On a related note, sexual repression stems from the idea that sex is a base instinct and not particularly safe or wholesome. Thus, sexuality is suitable only in very private and intimate circumstances. How far these tolerances are taken in art and media varies with the degree of guilt and repression of any individual. Male nudity strum these tight wires and therefore their images on screen will be met with varying degrees of discomfort as we are getting into deep waters where a lot of people simply are not prepared to deal with, especially from their entertainment. .
4. Sexual repression is transmitted vertically. Parents frequently want to transmit their attitudes on sex to their children in a highly controlled fashion. Sexual imagery and attitudes transmitted via the media will be met with substantial resistance by those parents who want to control how sex is presented in society at large. Nudity can be an issue for them.
With regards to homophobia, Kinsey saw a full spectrum of sexual flexibility even in males. But, homophobia is not triggered by the male phallus, especially a non-erect one, but images of homosexual emotional and physical intimacy. Viggo's junk in "
Eastern Promises" is not going to tweak any but the most extreme homophobe, while the tender scenes of making out between men will send a shudder to a greater swath of an audience, male and female.