Yeah, this. Free trade (voluntary exchange) is inherently non-zero-sum, because each side gives up what they want less in order to get what they want more. That cannot be zero-sum.
That is not completely true. The parties can incorrectly value the items being traded resulting in a non-positive sum trade for either or even both parties.
However, absent intentionally deceptive information (i.e. the overwhelming majority of modern advertising and marketing), that is expected to be fairly uncommon in total-value terms.
If your trading partner has the ability to manufacture something with a better cost structure than you can, say, because they have iron ore mine, a smelter and a gigantic hydro electric dam all in close proximity to each other, then you get a benefit from buying their cheap steel and performing the higher level manufacturing to convert that raw steel into goods that you can sell to other markets.
Now, if you self inflict 25% tariffs on that steel, you'll have to find other more expensive steel to replace the cheap steel previously imported from the neighbour. Maybe there's nowhere in your country that has the same confluence of inputs required to make steel as cheaply as your trading partner did. Now you've got a permanent cost disadvantage.
Or maybe you're just not willing to spend $20 billion to build a giant hydroelectric dam that gives you a cost advantage. How many decades of lost market share are you willing to give up before you think you might come ahead?
Thinking that trade is always zero sum is bullshit. There are benefits outside of the balance sheet of goods moving across the border.
How long do you think that other countries will wait until they decide to start taxing electronic services that the US sells so much of? Do you really think the short term gains of going after smelting steel are worth losing that market share? Blocking Google and Facebook is not all that hard to do.
People who peddle ideology love to sell complex problems as having simple solutions. Well guess what: we've built a society that is so complex that nobody understands how everything interacts. One thing is certain: everybody's going to hurt.
I think that only applies if people have the option of selecting the things that they actually want. From what I've observed it's more often the case that people don't give up the things that they value less for the things that they value more. Instead, they give up the only option they have to trade (e.g. labor at jobs that they despise) in exchange for the only option they can trade for to survive (e.g. products that keep them alive but provide little satisfaction).
