Donald Trump Jr. jumps into a Twitter fight between Alexandria Ocasio-Cortez and Barstool Sports' founder over employees' rights to unionize

• 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 consider unionizing. 
• 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.