Before singing "Desperado" for an encore Saturday night, Ronstadt called Moore a "great American patriot" and "someone who is spreading the truth." She also encouraged the audience at the Aladdin hotel-casino to see the documentary about President Bush.
Ronstadt's comments drew loud boos, and some of the 4,500 people in attendance stormed out of the theater. People also tore down concert posters and tossed cocktails into the air.
"It was a very ugly scene," Aladdin President Bill Timmins told The Associated Press. "She praised him and all of a sudden all bedlam broke loose."
Timmins, who is British and was watching the show, said he didn't allow Ronstadt back in her luxury suite afterward and she was escorted off the property.
Ronstadt's antics "spoiled a wonderful evening for our guests and we had to do something about it," Timmins said.
Ronstadt, 58, had been booked to play the Aladdin for only one show.
On Monday, Moore released a letter to The Associated Press that he intends to send to Timmins.
"For you to throw Linda Ronstadt off the premises because she dared to say a few words in support of me and my film, is simply stupid and Un-American," Moore wrote.
Calls to Ronstadt's manager were not immediately returned.
In an interview with the Las Vegas Review-Journal before the show, Ronstadt said, "I keep hoping that if I'm annoying enough to them, they won't hire me back."
Timmins said Ronstadt would not sing at the Aladdin again: "As long as I'm here, she's not going to play."
Moore said Timmins owes Ronstadt an apology.
"I have an idea how you can make it up to her -- and to the millions of Americans you have offended," Moore wrote. "Invite her back and I'll join her in singing 'America the Beautiful' on your stage. Then I will show 'Fahrenheit 9/11' free of charge to all your guests and anyone else in Las Vegas who wants to see it."