A Bonnaroo Dad's Guide to Justin Bieber

ABC News' Bill Weir reports:

The first time I met Justin Bieber, he looked like he had just arrived from The Magical Land of R&B Elves.

Still virtually unknown to U.S. audiences in 2009, "Good Morning America Weekend" was his version of "The Ed Sullivan Show" and the kid that walked in with his guitar was adorable beyond suspicion. Only a person who resents the cuteness of baby polar bears would question his motives or music.

Well, that pass has expired.

Because in the eyes of the law, the molten moppet is now a man. While his cherubic looks remain, Bieber is an 18-year-old multimillionaire who has seen things we can't imagine and still wields the power to turn armies of impressionable little girls into screaming, quivering puddles.

So on behalf of fathers of daughters everywhere, I went into our latest "Nightline" interview with a level of scrutiny reserved for a teenager carrying the nuclear codes. As long as his face gazes from my 15-year-old niece's pillowcase, I get to care about Bieber's tattoos, how he treats women and whether he actually punched a paparazzo last month, as reported.

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"I can't really talk about that," he said.

But before we try to peer past his politely well-guarded facade to get a glimpse of true character, there is something else all you Bonnaroo Dads and Coachella Moms also have the right to judge: Justin Bieber's music.

"A lot of people will just, you know, they'll hear my name and they'll just be like, 'oh, I'm not going to buy that,'" Bieber said. "But if they just take the time because it's different and it's new and I think it's - I think people will really be surprised."

Fair enough. If the Beatles can go from " Love Me Do" to the White Album, maybe Bieber can surprise us too. It just won't be with "Believe," an album that moves his career from the flirting-at-recess stage to the flirting-in-the-18-and-over-club stage. The tracks have more bass, his voice has more falsetto, but layered on top are still the kind of non-threatening lyrics that have been sending shots of dopamine into young female brains since Donny Osmond.

"I could be a gentleman, anything you want," Bieber promises over a syncopated beat. "If I was your boyfriend, I'd never let you go." Simple, yes. But effective. Co-written with Mike Posner, "Boyfriend" debuted at No. 2 on Billboard's Hot 100 last month.

"My music is definitely developing," Bieber said. "I'm growing up. I'm becoming a man. I'm maturing. My fans are growing with me. So when they say, 'do you think you're trying too hard to grow up and you're fans are going to understand?' you know, they're growing with me, so I think that they want to change as much as I do. I think it's definitely a good change."

For a kid raised first by a young, single mom in Onatrio, Canada, and then by a team of handlers while touring the globe, outward signs of rebellion are amazingly hard to find. Bieber is on the record saying he has no intention to ever try drugs, much less empty any mini-bars or trash any hotel suites.

"You just have to be responsible," he said. "Don't drink and drive and, excessively. I think you just have to be responsible."

He now has control over his vast fortune, but aside from smartly investing in a few tech start-up and setting up some trust funds, Bieber said he has yet to go on any Michael Jackson-sized shopping sprees. And even when he gets a tattoo, it's the sort of ink that would make his Born Again mother proud.

"Yeah, it's Jesus on my calf," he said, smiling. "I'm never gonna get tired of seeing Jesus' face on the back of my leg. So I, I thought it would be a good tattoo."

One of the most candid moments of our interview came when a shapely young woman mistakenly wandered onto our set. "You can walk by any time," he replied in red-blooded splendor. When I ask if he's had that first lightening-strike, buckle-your-knees bout with love yet, he remains vague.

"I'm still finding out what love is every day," Bieber said. "I'm loving and I think it's great being young and finding that love, and learning and it's fun."

And he bristled when defending his choice to keep his relationship with Selena Gomez off-limits to fans and press.

"What does that have to do with my career? It has nothing to do with my career," Bieber said. "Me being in a relationship has nothing to do with my songs because my songs have - every song I write is not about my relationships. My songs I write are about my fans, about experiences that I go through, experiences that I want to go through.

"So I think that, you know, if I start making it about that, about who I'm with and then, that's when my fans are going to start resenting me," he continued. "When I'm like, we're so in love-they don't want to hear that as much as I don't want to talk about that."

Bieber did admit he found musical inspiration from Mariah Yeater, the woman who falsely accused him of fathering her child during a random backstage hook-up last year.

"It's like, why should I have to do this?" he said, describing his reaction to calls for a paternity test. "Like am I going to have to do this every time someone says it? I was like, this is ridiculous. But I just wanted it to be over so by the time it was dragged on, I was like fine, I'll just take it. This is ridiculous and so I took it and it was fine."

And he got a song out of it. For the rabid Michael Jackson fan, the song "Maria" is Bieber's "Billie Jean."

"Everything happens for a reason. That's what I like to say," he said.

And that was my biggest take-away. Bieber really believes that he became famous for a reason, and seems to respect the power he carries. Just as importantly, the management team around him has done an admirable job teaching him to give back.

And while it would be nice if Bieber threw in a Led Zeppelin or Neil Young cover for the all the dads who bought the tickets for his tour, of course it's fine if he doesn't. For now, he makes your little girl happy like few things can. And those little girls could be in love with a lot worse.