Up until the point that access to Trump's tax returns was mentioned the article was warning about the false privacy associated with anonymizing identity.
I can understand the argument that candidates should reveal their financial history. But that doesn't mean otherwise reasonable concerns about false anonymity should be suspended when talking about the anonymity of one particular person who has explicitly asserted their privacy rights.
Even if you think the authors were making a more general statement about all candidates and not just Trump, that seems like a terrible argument to me. In the cases of candidates for office, voters are free to penalize candidates who don't reveal enough information about themselves by not voting for them. There is no need to soften any privacy concerns about anonymized identities.
Compare these two hypothetical scenarios:
1 - Voters don't have access to the candidate's tax records
2 - Due to released tax records, the voters know for certain all of the below facts about the candidate: A - The candidate paid no taxes, B - The candidate cheated on their taxes, C - The candidate is not as rich as they claim to be, D - The candidate's businesses lost money so they're not as good a businessperson as they claim to be
In the first hypothetical scenario the voters the voters know there's a possibility that the candidate might be hiding something, in the second hypothetical scenario the voters know for certain that the candidate is a lawbreaking, tax cheating, lying hypocrite.
In which of these hypothetical scenario do you think the voters are going to penalize the candidate more?
A released tax records B released tax records C didn't release any records
FWIW, I've talked to an accountant about the idea of Trump revealing his tax records and the bottom line is that they would be sufficiently complicated that there is no possibility that the average person would be able to interpret them accurately, so you'll be left with the spin from the various media organizations, hardly a source of objective truth.
So I would assert that requiring candidates to release their tax records doesn't actually provide any useful information for a voter.
Remember that Trump's tax records, are already examined by the IRS and I believe have been audited. So there shouldn't be any question of illegal activity being hidden, unless you want to assert that the IRS can't be trusted either.
There are also other concerns about tax records revealing information about 3rd parties. And finally tax records aren't really a useful way to understand the intricacies of a business. If you are really interested in that you would want the audit report for the underlying business and not just tax records.