Former Vice President Joe Biden Joe BidenBiden says voters should choose who nominates Supreme Court justice Trump, Biden will not shake hands at first debate due to COVID-19 Joe Biden should enact critical government reforms if he wins MORE slammed President Trump Donald John TrumpBiden says voters should choose who nominates Supreme Court justice Trump, Biden will not shake hands at first debate due to COVID-19 Pelosi: Trump Supreme Court pick 'threatens' Affordable Care Act MORE for criticizing teenage climate activist Greta Thunberg, saying, “What kind of president bullies a teenager?”

Biden said Trump could learn from the 16-year-old, who was named Time's "Person of the Year," after the president targeted her in a tweet.

“What kind of president bullies a teenager?” the presidential candidate wrote. “@realDonaldTrump, you could learn a few things from Greta on what it means to be a leader.”

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What kind of president bullies a teenager? @realDonaldTrump, you could learn a few things from Greta on what it means to be a leader. https://t.co/18Y6uZexMC — Joe Biden (@JoeBiden) December 12, 2019

Biden’s tweet came in response to a post from the president telling Thunberg to work on her “Anger Management problem” and to “Chill.”

So ridiculous. Greta must work on her Anger Management problem, then go to a good old fashioned movie with a friend! Chill Greta, Chill! https://t.co/M8ZtS8okzE — Donald J. Trump (@realDonaldTrump) December 12, 2019

Thunberg updated her Twitter bio in response to Trump's remarks, now describing herself as a “teen working on anger management.” The president’s campaign also edited his photo to replace Thunberg on the magazine cover and tweeted it Thursday.

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