Bradley Cooper doesn't understand why many of his fans were irked by his appearance at this year's Democratic National Convention.

Cooper's conservative fans were upset with him for attending the DNC because of the actor's portrayal of the Navy SEAL Chris Kyle in 2014's "American Sniper."

"I was not expecting that," Cooper said when asked about the backlash on the "The Late Late Show With James Corden." "Republicans were up in arms that I was there watching the president speak."

Some Twitter users said at the time that they plan to boycott Cooper's future films over his presence at the convention. 

The complaints have been mocked by others who say Cooper was simply acting a role when playing Kyle and conservatives shouldn't be surprised.

Cooper earned an Oscar nod for "American Sniper," which became a blockbuster thanks in part to an enthusiastic reception among conservative moviegoers.

The Associated Press contributed to this report.