Edward J. McCaffery is Robert C. Packard trustee chair in law and a professor of law, economics and political science at the University of Southern California. He is the author of " Fair Not Flat: How to Make the Tax System Better and Simpler ." The opinions expressed in this commentary are solely those of the author.

(CNN) Like a spoiled toddler, Donald Trump pouts, yells, lies and makes excuses when he doesn't want to do something. Trump often counts on the ignorance of others to help get away with his deceptions. Perhaps this is why he loves the poorly educated in his shrinking base.

The Donald is doing his customary dissembling with his tax returns. Warren Buffett has now joined the chorus asking for some transparency. The "Oracle of Omaha," who says his tax returns like Trump's are under audit, offered to share his filings along with Trump's at a meeting -- any time, any place, before the election -- where the public could ask questions of both billionaires.

Buffett has previously voluntarily disclosed information about his tax returns, leading to the proposal for a " Buffett Rule " that Hillary Clinton, along with Buffett himself, supports, and which would raise taxes on millionaires including Buffett. Buffett's returns showed he is a fairly simple investor, who avoids higher taxes by holding onto (not selling) his Berkshire Hathaway stock, and who lowers his tax rate by making charitable donations.

What tax returns of Trump's we have seen , from the late 1970s, show that he aggressively attempted to pay no taxes by reporting little or no income, using tax breaks typically afforded real estate wheelers and dealers. The Buffett Rule would not have affected Trump's disclosed tax returns because he has never shown that he has earned $1 million in any year.

But Buffett's point is not about what taxes Trump does or does not owe. It is about what information about himself that Trump, as a billionaire asking the people to elect him president, owes the public. Now let us put this in language that Trump himself might understand:

There is NO legitimate reason for Trump not to release his tax returns. Sad! There is only one word for Don't-Disclose-Donald's position: Unacceptable!

Let's go through the excuses:

He's being audited, so he cannot disclose

This one is easy. He can. There is no legal bar to releasing returns while under audit. Richard Nixon did so. Trump himself has released his returns in other contexts while under audit. This one is just wrong. Period, as Paul Ryan might say (or write).

He's being audited, so he should not disclose

This one is easy, too. Trump has implied he shouldn't release his returns because the public glare might lead to the Internal Revenue Service learning of issues that it might otherwise have missed, and some in the media have fallen for this excuse. But this reason is bad, because, aside from its implausibility (Trump banking on the incompetence of the IRS), it is just a matter of Trump's money. Clinton and all other presidential candidates for 40 years who have released returns have run the risk of triggering an audit. That's part of the price of running for office. Period. Trump doesn't want to pay the price. But that shouldn't really be his choice; the people ought to set the terms of this deal of getting elected president. Buffett pointed out that he too is being audited by the IRS, so he has taken even this argument away from Trump.

There's nothing to learn

Trump apologists often state or imply, like Trump himself has, that there is nothing to learn from his tax returns. This one is easy to answer, too: Let the public decide. Plus learning "nothing" is "something": the people would surely like to know if Trump's tax returns are unobjectionable. It's a self-serving and offensive explanation. Period.

The public doesn't care

See above: This is another self-serving and offensive explanation. Let the public decide if it cares when it has the facts to know if it should care or not. Period.

Mitt Romney's 'little sentence'

This wouldn't be a commentary on Trump unless we got to something truly odd. Here it is: Trump is now arguing that the release of Mitt Romney's tax returns -- which Trump himself called for, and which came in January 2012, not "right before the election," as Trump is now saying -- might have cost Romney the election, because of " one little sentence that they found." This one is bizarre. First, Romney was hurt by the revelation of his low effective tax rate, a fact of which Trump has already boasted. That's a matter of math, numbers, not a "sentence."

On the not-heroic leap that Trump is thinking of himself even while talking about others, can it be that there is some kind of "sentence" in his tax returns that might "cost him the election"? What could that be: a disclosure of some aggressive investment position, a list of charitable contributions, evidence of involvement with foreign or unsavory entities? If, as Trump himself has said, the public doesn't care, and there is nothing to learn from his returns (see above), what could this sentence be?

Note well the structure of Trump's "logic": There might be a sentence in my tax returns that could cost me the election, but it would only be because people (such as the "dishonest media") made a big deal about the "little sentence" and misunderstood it, so it would be sad, because I really should be president -- I will make America great again. I alone know what is important about me. I must help the people by not revealing facts about me that they would misunderstand. And not even Warren Buffet could possibly understand.

That's not how democracy works; it's how dictators behave. Period.

Sometimes the truth hurts. But in a democracy, our leaders are subject to the truth as the people see it. Period. Don't-Disclose-Donald has no excuse for not disclosing his tax returns, and his statements on this issue, as on so many others, reveal very deep and dark problems with his attitudes toward democracy. Period.