Both sides (Trump/NYT) have a vested interest in their side of the story.
In a way. The NYT has a vested interest in doing it's job so they get paid for doing it.
Trump has vested interests in not doing his job (which might well be helped by keeping his taxes secret in opposition of custom) and getting paid for not doing it.
btw. In Sweden you can see the taxes of everyone and it is generally agreed that this is good.
And public interest doesn’t make an action or decision legal or ethical.
Actually it does in many cases. Take photos. If you are Dishwasher A, people are not allowed to make photos of you and distribute them. If you are President B (or actor C), they are. Because of public interest.
What is ethic or legal can change dramatically even in a matter of decades - or places in the world, see Sweden.
In the middle ages it was blasphemy (official church position) to not share knowledge. 1710 saw the invention of the word "copyright" as a censoring tool after the death penalites the church had pressured upon France were not effective enough to prevent idea sharing.
Which btw. led to a very heated debate amongst the founders if a copyright or patents should be allowed at all in the new United States, which led to the "only for advancement of science" clause in the constitution, which got so heavily violated with all the term extensions...
I don't see any moral reason for holding anyones taxes secret beside maybe a very low key "it's private". I mean, most people even love to show their finances (or lack thereof) to the public by driving big trucks and living in an oversized mansion!!
Can anybody explain a reasonable argument for why taxes should be secret?