I've noticed that Japan (maybe other places) have this thing where idols and some games (in my experience visual novels) put you as the main person of interest. So when the idol sings I love you, they mean you. Or the fact most anime and VN protagonist are super bland and can be blank slates for us to get immersed in the universe. So when they say to keep her pure, it's mainly for the popularity same. Like she's there for "you," and only you. "A pure maiden" for you to admire. Kinda explains why it's seems easy to get obsessed with some of the media there.
The idea, from what I understand of Korean and Japanese Idol culture, is that a public figure belongs to the public. You have to be a role model, an ideal. Doing anything to screw that up (have an affair, get pregnant, get married without telling your fans, get discovered in a relationship), is totally unacceptable. Idols always have to be available to their fans, as their fame stems from them. It's kind of twisted in a way. But that's slowly been changing. Too slow, but still. (=・ω・=)
I don't know what's up with Japan and there idea of idols being pure. American idols are far from the "pure" idea. And plus she doesn't even want to be an idol she just wants to do the things she loves boxing and that one dude, so leave her alone creepy mayor!!!