President Trump weighed in on a widely criticized joke made on Twitter by a writer for “Saturday Night Live” about his 10-year-old son, Barron, calling the writer “terrible” and the incident “a disgrace” in an interview broadcast Thursday night on Fox News.

In the conversation with Mr. Trump, the Fox News host Sean Hannity described Barron as “a wonderful, smart, charming kid,” adding: “And then, they attack him. That’s got to hurt you and Melania.”

Mr. Trump replied: “Well, ‘Saturday Night Live’ — a person from ‘Saturday Night Live’ was terrible. It’s a failing show. It’s not funny. Alec Baldwin’s a disaster. He’s terrible on the show and, by the way, I don’t mind some humor but it’s terrible. But for them to attack, for NBC to attack my 10-year-old son —”

Mr. Hannity said, “Horrible.”

Mr. Trump continued: “It’s a disgrace. He’s a great boy. And it’s not an easy thing for him. Believe me.”