Metro

WATCH: Bieber launches anti-cyberbullying PSA after ‘09 LI mall frenzy

Justin Bieber cut a plea bargain — and then pleaded with fans to fight cyberbullying.

The pint-sized pop sensation collaborated with Nassau County DA Kathleen Rice to drop a public service announcement today, aimed at helping kids fight cyberbullies and avoid other Internet traps.

Bieber did the 11-minute, 10-second PSA to take the heat off manager Scott Braun and Def Jam Records executive James Roppo.

The suits had faced misdemeanor charges in connection to an out-of-control mob of 3,000 girls that came to get the Bieb’s autograph in 2009.

Bieber never came out for the event, and police said Braun and Roppo refused to help disperse the screaming mob at Roosevelt Field in Garden City.

In the PSA, Bieber sat at a high-leather backed chair and wore huge glasses, a white T-shirt and denim coat. He told potential cyberbullies not to make a “small mistake that could follow you for the rest of your life.”

Bieber, 18, then did a one-on-one interview with a surprised fan, who described how she was bombarded with hateful instant messages after getting into a fight with a seventh-grade pal.

“Kids are mean and they don’t realize how hurtful what they’re saying can possibly be to the person they’re saying this stuff to — cause to them, it’s just a word,” Bieber said.

“Sometimes you’d rather be physically beaten up than emotionally damaged.”

The tiny hitmaker said he knows what it’s like to be bullied.

“I was picked on,” he said. “It’s a tough feeling. But at the end of the day, you can get through it.”