Olivia Wilde Reads Justin Bieber Fans' Mean Tweets on 'The Tonight Show' (Video)

Olivia Wilde Justin Bieber Split - H 2013
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Warning to celebrities: if you mock Justin Bieber on Twitter, Bieber-maniacs will hunt you down and launch an assault of mean tweets.

The Black Keys' Patrick Carney learned this the hard way recently, when he baited fans of the Biebs by questioning why the 19-year-old pop star would publicly pout over being snubbed by the Grammy Awards. And several days ago, actress Olivia Wilde stirred up another cyber-attack when she tweeted that Bieber -- photographed shirtless on the streets of London -- should put his "f----ing shirt on."

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Wilde, who stars in the upcoming comedy The Incredible Burt Wonderstone, joked Tuesday on The Tonight Show that "about 35 million" furious Bieber followers replied to her tweet. Among the most memorable responses: "Are you a lesbian or are you too old?" and "Put your shirt over your mouth!"

Meanwhile, Bieber's European meltdown was unfolding in the British capital, where he started a concert two hours behind schedule -- inciting boos from the crowd -- and lunged at photographers while being restrained by his bodyguard. He also removed his shirt a lot.

"It's so cold there and I was concerned," Wilde told Jay Leno. "You know, I have a 19-year-old brother in London and it's freezing and if I saw him without a shirt, I would tell him to put it on. So I told Justin Bieber, 'put your f----ing shirt on' ... with love."