Treasury Secretary Steve Mnuchin on Sunday defended his boss, President Donald Trump, who recently lashed out at professional athletes who refuse to stand during the national anthem.

During an interview with ABC News, Mnuchin compared the protest to the NFL's rules against stickers on players' helmets.

"The owners should have a rule that players should have to stand and have respect for the national anthem," the treasury secretary opined. "This isn't about Democrats, this isn't about Republicans, it's not about race, it's not about free speech. They can do free speech on their own time."

According to Mnuchin, Trump has a right to call players who took a knee "sons of bitches" because "the president can use whatever language he wants to use."

"Is it not about the First Amendment?" ABC host Martha Raddatz asked.

"No, it's not," Mnuchin insisted. "They have the right to have the First Amendment off the field."