- Cooper attended the DNC with his mother and his girlfriend
- Many fans lamented the fact that the actor is not a Republican
The Oscar-nominated actor told "The Late, Late Show"
Tuesday he was surprised by the backlash he received from fans after the actor attended the DNC in Philadelphia last week.
"I was not expecting that. I took my mom, and we went to hear the President speak," Cooper said. "It was just unbelievable."
"The Republicans were up in arms that I was there listening to the President speak," he added.
"American Sniper" is based on an autobiography by Kyle -- a former Navy SEAL who was murdered in 2013 by a former Marine who suffered from PTSD at a shooting range in Texas.
Kyle became a conservative icon, known for his staunch support for gun ownership rights. So when Cooper attended the DNC many fans lamented the fact that the actor is not a Republican.
While the movie's director, Clint Eastwood, is known for his right-wing views, Cooper is a supporter of the Democratic Party and told "The Late, Late Show" that President Barack Obama has been "incredible."