The answer, obviously, is the explicit nature of the lyrics ("Sex in the air, I don't care, I love the smell of it/Sticks and stones may break my bones/But chains and whips excite me"). Loud is full of brazenly frank sexual content, but somehow that hasn't really been an issue until now, when there's a video driving home the point. And yes, those are some pretty unambiguous concepts we definitely would rather our ten-year-old cousins are not shouting from the backseats of cars. But there are plenty of equally raunchy things they're already shouting without a raised eyebrow.
Rihanna's tweet about her relative nakedness here is interesting: when the song is less direct or the deviant behavior is couched in metaphor, no one even thinks twice. And Rihanna saying she likes a little S&M is no less appropriate than Nickelback's Chad Kroeger saying, "I like your pants around your feet/And I like the dirt that's on your knees/And I like the way you still say please/While you're looking up at me/You're like my favourite damn disease." Actually, as a moral compass we'd much, much rather follow Rihanna than Kroeger. At least there's no ugly subservience with Rihanna -- when she's leading Perez Hilton around on a leash it's clear they're both having fun.
