No, of course. actors are not brainless. Actors are very good at reciting the script in a totally sincere and convincing manner. That is a talent, and it requires rather a lot of practice to master. But of course, it means that they are good at being insincere while pretending to be sincere. Michael J Fox played a dippy young Reaganite and his personal views were nearly the opposite. Carol O'Connor was the opposite of Archie Bunker, and Edith Stapleton was very far from being a dingbat.
Before Reagan entered politics, he gave pro-corporate anti-union speeches for the National Chamber of Congress all over California. Unlike Fox and O'Connor, he began to actually believe his own bullshit. And that was when they decided to trot him out for governor.
Of course, he had previously ratted out the members of his union,the SAG to the House Unamerican Activities witchhunts.