CANNES, France—More than 20 years ago, Marilyn Manson created his persona and even booked his first performance without even having written a song. Best of all, he wrote his autobiography before bothering to get famous.

At the time, this cart-before-horse approach to personal branding was novel to the point of bafflement. But in today's world of highly curated, meticulously sculpted social media identities for which actual accomplishment is optional, that kind of debut would just make him part of the aspirational herd.

"Having a persona online doesn't make you a personality now," he told a packed audience at the Cannes Lions. "When everyone can be famous, to me it's not a challenge. The best will rise to the top."

Speaking at the agency Grey's annual music seminar during the global advertising festival, a sedate and reflective Manson discussed his views on everything from the creative process (he likes to sit in a dark dressing room for three hours at exactly 65 degrees Fahrenheit before each performance) to his ongoing quest for new fans (he hopes each album will appeal to "people who've never heard me before or didn't like me before").

But he spent much of his conversation with Grey creative chief Tor Myhren talking about his decades-long troubled relationship with the media, which has largely focused its coverage on his high-profile romantic relationships and his music's supposedly malicious impact on young listeners.

Manson was famously (and falsely) accused in some mainstream news outlets of inspiring the perpetrators of the Columbine High School massacre to commit their killing spree. At Cannes, he pointed out that the killers, Eric Harris and Dylan Klebold, actually weren't fans at all and reportedly felt Manson's music was "too pop."

"With Columbine, it really shut down my career entirely, to the point where casinos—gambling establishments—refused to book my shows," Manson said.

Rehabilitating his reputation was a slow and incomplete process, one that left him bitter about the hypocrisy of news outlets that would demonize his music while prominently featuring criminals.

"They put these two killers (Harris and Klebold) on the cover of Time magazine," Manson said. "I've never been on the cover of Time magazine. That's the whole point."

For Manson, the Columbine experience, along with other consistently arising controversies throughout his career, has been one side of the coin he forged when he decided to invent a terrifyingly seductive persona in the early 1990s. On the plus side, he could create an artistic and provocative image from whole cloth, but at the same time, parents and pundits could project their own fears onto his invented identity.

The price of persona is well worth it to Manson, who said he has always valued his role as a polarizing character over his actual artistic output.

Now respected in several circles for his talents as a musician, actor and even painter, Manson said his biggest concern is the idea of becoming too palatable.

"I wonder sometimes if I've outgrown my spotlight," he said. "Someone asked me a long time ago, 'Are you worried your image will overshadow your music?' No, I'm worried my music will overshadow my image."