I can kind of understand it if you consider having a stable, strong steel and aluminum industry a national security issue.

Say Canada pulls an Uber and just drives all US forges out of business with Uber cheap metals. Though I doubt we have thay much production capacity to actually put the US at risk.

What gets me is the hypocrisy of the US. If it's a US industry/company under threat then it's a national security issue. If a foreign country has any protectionist policies, then they're communists and subject to sanctions and/or invasion and/or having their government toppled.

I guess it's pretty straightforwardly self-serving, but surely all the other countries' economy's who get carelessly trashed constitute a bigger national security issue!

I think the mistake you're making is that the protectionist policies of (say) the US and China are not remotely comparable. In particular, the whole reason the US needs steel and aluminium tariffs is that China has used protectionism and state subsidies to build a steel and aluminium industry so far in excess of what the country consumes that the surplus has tanked global prices. This is pretty much unprecidented. The US is not the only country that objects to this; the EU wanted to put tariffs on China a few years earlier but they couldn't agree on which goods the tariffs should apply to.

They do it because the people who vote for them eat it up. Politics is basically the "science" of hypocrisy. All you need is an easily impressionable audience, ideally with plenty of preconceived notions.

https://i.redd.it/gye28fevde011.jpg

Your analysis of American politics makes it sound like the entire voting block of US adults supports these policies, wanted this man as president, and watches Fox News. Fact of the matter is 3 million more people voted for the other candidate but this guy won on a technicality. The majority of Americans do not support these policies but our representative election processes are designed to prevent simple majority rule. Couple this with a legislative branch that cedes authority to the executive over the course of decades in the name of political expedience and we are where we are today.

I would argue that nowadays it could be framed as a "minority of Americans". [1]

1. https://www.nytimes.com/2019/08/07/upshot/trump-approval-rat...

Even if Canada is not likely to become an enemy, their metal industry could dissipate due to any number of other causes (just like how ours has dissipated). It's like using software dependencies - in the long term it can be better to cultivate your in-house engineers and their packages even when popular well-maintained libraries are out there.

If protectionism is good, then why did the world move away from it when it did?

I ask this question in good faith: global trade definitely has its downsides, but one positive aspect it has is that reduces the probability of armed conflict taking place between countries trading with one another. All else being equal, waging war on a customer deprives one of their business, and waging war on a supplier deprives one of that source of supplies.

To your point, cultivating your in-house engineers on a given project means that those engineers are tied up in that endeavour as opposed to working on something that has a higher return on investment.