I think that you are also right re their mental abilities to understand these complicated issues. So they develop a mantra and use it like one of the 10 commandments. The problem is that in these issues, often there are so many issues and shades of variance in each issue like this one re the steel tariffs. You can't have a simplistic mantra for everything in life. Our forefathers didn't intend for mantras that if followed blindly could lead to damaging your self or even suicide.
Then, they try to make these things a moral issue like you will go to hell if you ever have a tariff. Then this repels a who lot of voters who are looking for some common sense instead something written on stone from a higher source.
What angers them is GW is not bound nor locked in with this jingo mantra thinking. He will not allow a small group of people to put him and American into a box and then punish us when we try to get out of their pre conceived box.