You also have to keep in mind that this type of censorship doesn't have a direct relationship to the Japanese views of sex, which are traditionally rather liberal (when compared to Western Christian traditional 'sex=devil' sort of view). So, that's why you'll see sexual themes even in kids' anime sometimes. There's no huge stigma associated with sexual activity and primiscuosity there - it's sort of a 'well, whatever, do it if you feel like' approach. They don't really see any reason to hide it; the Buddhist/Shintoist religion doesn't concern itself much with sex, and the culture is only happy (wouldn't we all?)
But showing genitals is rude. Paradoxical?
Hey, I'm not the one who made it up

The Birds are using humanity in order to throw something terrifying at this green pig. And then what happens to us all later, that’s simply not important to them…