Economic theory is a hard sell when there are more practical issues that people are faced with.
To a blue collar worker, there's nothing more tangible than the factory you've worked at for most of your adult life, packing up operations and moving overseas or simply shuttering in the face of what appears to be, by design, a purposeful effort to make it nearly impossible to operate in the USA while simultaneously welcoming (out-right encouraging) the influx of cheap goods produced overseas in near-slavery conditions. (which has an added benefit of masking the declining value of the US Dollar, so . . . there's the motive, at least as far as the government's concerned).
We throw out the word "protectionist" far too liberally.
These people are not fat cats with monocles, top-hats, and ridiculous sideburns, rolling tobacco in $100 bills and smoking it up.
They're people who actually want to work. They know what they're good at (these dirty, inferior jobs like machining, welding, etc). It's no easy thing to just forget everything you've ever done and pick up an entirely new line of work. To add to it, there's far more people in those situations than there are opportunities to alleviate their conditions. And I swear, it's by design.
Entire towns have evaporated when factories shut their doors. In most cases, they never recover. Former workers fall into depression, turn to drugs, alcohol, etc. Crime rises. The next generation moves out in search of opportunity—that is, if they're fortunate enough to not get trapped in the life themselves. Give up the last bit of pride you have for a welfare check, and join the club. That seems to be the plan, anyways.
Tariffs are not the worst of evils. And telling people that they're just hurting themselves by supporting tariffs, when these people don't have any paycheck to spend anyway, and have this 'what's the fking difference?' look on their faces while you try to school them on economics . . .
It's hard to sell it.