Earlier quoted context omitted.
He would have to convince the courts that I don't like having a trade deficit with anyone somehow means our trading partners are "placing a burden or disadvantage upon the commerce of the United States by any of the unequal impositions or discriminations aforesaid"
He doesn’t have to convince the courts of that. The President makes foreign policy, not the courts. As long as the President is plausibly exercising a foreign policy power Congress gave him, the courts don’t get to reweigh the evidence and decide for themselves whether the trade deficits result from other countries placing trade barriers or something else.
The courts aren’t making foreign policy. That’s a strawman argument.
The President also doesn’t have unlimited powers. It’s President, not King or Dictator.
The President must act within the powers granted by law. The court has determined this act was outside of the law.