A Fox News segment about climate change grew heated after a conservative commentator called teen climate activist Greta Thunberg a "mentally ill Swedish child" who is being exploited globally by the Left.

Discussing how the idea of having "Meatless Mondays" was not helpful to the environment, the Daily Wire's Michael Knowles said, "If it were about science it would be led by scientists rather than by politicians and a mentally ill Swedish child, who is being exploited by her parents and by the international Left."

Chris Hahn, a former aide to Senate Minority Leader Chuck Schumer, issued an immediate angry response, saying, "You're a grown man and you're attacking a child. Shame on you."

When Knowles tried to respond, Hahn continued, "Relax, skinny boy! I got this. Okay? You’re attacking a child, you’re a grown man. Have some couth. Maybe on your podcast you can get away and say whatever you want because nobody is listening. You're on national television, be a grown-up when you’re talking about children.

"She’s trying to save the planet because your president doesn’t believe in climate change; and kids need to take to the streets to worry about their future. You are despicable for talking about her like that, and you should apologize on national television right now," Hahn continued.

"I think the international Left and her parents, who are exploiting a girl with many mental illnesses ..." Knowles began.

"You call her mentally ill! Take it back now! Take it back now!" Hahn interjected, again calling Knowles "despicable."

Greta and her sister Beata have been diagnosed with a form of autism, ADHD, and other conditions. Thunberg has called her condition "a superpower" that allows her to address climate change more effectively.

In a statement to the Washington Examiner, a Fox News spokesperson said, "The comment made by Michael Knowles who was a guest on The Story tonight was disgraceful – we apologize to Greta Thunberg and to our viewers."