It seems like there are 3 basic arguments made for tariffs:
1. You want to protect industries in your own country from competition that is cheaper because they use lower wages. So you’re putting a tax on consumers in order to dissuade them from purchasing the less expensive overseas product. This has been the traditional argument. The problem is that the government is creating an artificial higher price that is not reflective of actual value, and essentially the government is attempting to redistribute wealth. The other problem, of course, is that other nations whose products are targeted in this manner will retaliate by targeting our exports as well, which we are seeing happen.
2. The second argument is a variation of the first one but in a reverse way: the politician doesn’t propose new tarrifs but he rejects new free trade agreements because he is concerned about making things worse for workers. This would be closest to Bernie Sanders’ position. He is opposed to lowering existing trade barriers, but also opposed to new barriers being erected.
3. The third argument is that tarrifs are awful, but other nations are imposing them already. If we threaten to impose them ourselves we can therefore scare the other nations enough to lower theirs in order to stop us. Our real goal is to actually have freer trade than we have now.
This last appears to be Donald Trump’s approach, though he only hints at it- other members of his administration are more explicit. What’s interesting is that Wall Street is not only convinced that this is exactly what Trump is doing, they are also convinced he will succeed, and that’s the sole reason the stock market hasn’t tumbled off a cliff thus far. And the truth is that Trump might succeed, because there is not a single nation trading with us on this planet, including China, which is not more reliant on our trade than we are on theirs. We hold the upper hand. The problem is that when you’re dealing with the pride of other nations it’s a huge gamble. China and other nations may be willing to suffer much before they’ll give in to demands made at what they regard as the barrel of a gun. We’ll have to see.