• Trump Jr. called Ocasio-Cortez's criticism of Portnoy "the biggest mistake she's ever made on Twitter."
  • Earlier Tuesday, Ocasio-Cortez accused Portnoy of "likely breaking the law" by threatening to fire "on the spot" employees who expressed interest in creating a union at the sports site.
  • The US Department of Labor also waded into the Twitter debate, tweeting out its hotline number in response to Portnoy's threats.
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Donald Trump Jr. jumped into a Twitter fight on Tuesday between Rep. Alexandria Ocasio-Cortez and Barstool Sports founder David Portnoy over Portnoy's threats to fire employees who express interest in unionizing.

The president's eldest son cheered on Portnoy, who challenged Ocasio-Cortez to a debate on Twitter after the New York Democrat said his comments "likely" violated US labor law.

"Picking a fight with @stoolpresidente and @barstoolsports is probably the biggest mistake @AOC has ever made on Twitter," Trump Jr. tweeted . He later added, "This should be fun" with three popcorn emojis.

Portnoy quote-tweeted Trump Jr., writing"When will Alexandria O'CRAZIO Cortez @Aoc learn not to tangle with our countries Presidents? @realDonaldTrump."

Read more: Barstool Sports' Dave Portnoy threatened to fire employees in anti-unionization tweets and challenged AOC to a debate on Twitter

Portnoy on Tuesday shared a 2015 blog post he wrote in which he said he hoped Barstool's employees would unionize "just so I can smash their little union to smithereens." He was prompted to share his thoughts on unions after employees at the sports site Ringer announced their plan to form a union.

Barstool is known for its often insensitive content, which has included a blog post making crude jokes about a missing female college student who was later found murdered. Last year, Portnoy was widely criticized for telling a 20-year-old female employee that she would be too ugly to appear on camera in five years.

In another tweet , Portnoy said he would fire "on the spot" any employee who reached out to a reporter who'd offered advice on unionizing to Barstool employees.

Ocasio-Cortez jumped in, pointing to the National Labor Relations Board's determination that it's illegal for employers to discourage employees from conducting union activities.

"If you're a boss tweeting firing threats to employees trying to unionize, you are likely breaking the law & can be sued, in your words, 'on the spot,'" Ocasio-Cortez tweeted at Portnoy.

The US Department of Labor also waded into the Twitter debate, tweeting out its hotline number in response to Portnoy's threats.

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SEE ALSO: Barstool Sports' Dave Portnoy threatened to fire employees in anti-unionization tweets and challenged AOC to a debate on Twitter