Many will disagree, but the most fascinating question in life is “why” — why do people, good and bad, do what they do?

The “why” question surfaced this morning when the Angry Left downtown threw another adult tantrum.

The hate-obsessed Los Angeles Titanic carried a bizarre, dishonest review of the latest I Hate Sarah for Irrational Reasons tome by the newspaper’s main critic, the equally obsessed David Ulin.

Even the Angry Left concedes — off-stage —that the still unreleased book, The Rogue, is an undisguised small-time hit piece against Ms. Palin. Nothing else. As distinguishable as a blade of grass in a meadow.

The author formerly was a legitimate writer. He veered off into the supermarket tabloid, quick buck-type dodge, blowing his rep on sensationalist tales. Now, as a senior citizen aching for a payday to restock his hollow wallet, he is desperate to cobble together his once- respectable reputation.

A Palin book straight off the supermarket’s lowbrow You Won’t Believe the Cow Jumped Over the Moon shelves looks like another ill-chosen career move by Joe McGinniss.

Our subject this afternoon, however, is the devious Mr. Ulin, not the unfortunate Mr. McGinniss.

By the end of Mr. Ulin’s lengthy review of the spying-on-Sarah book, I felt foolishly betrayed by what should have been a predictable denouement.

The headlines suggested a fair review:

“Flawed Look at Sarah Palin”

“Damning revelations are undermined by Joe McGinniss’ use of unnamed sources”

The thrust of the 322-page book is that Sarah Palin is one of the worst parents and personalities on the planet. She committed very pop culture sin except murder.

How do we know this?

We don’t.

As closely as I can tell, all but two of Mr. McGinniss’s sources are blind, and the two named hold an animus against Ms. Palin.

Unless your death is imminent and purple carrots are protruding from each ear, why would you bother with this unsubstantiated trash?

Here is how Mr. Ulin deceptively opened his review, hoping to mute his own Angry Left convictions.

I should have known better. I should have been at least suspicious.

While Mr. Ulin was critical of Mr. McGinniss’s scores of unsupported and outrageous assertions about Ms. Palin — like a true unquenchable hater, he listed all of them.

As if to say,

“Here’s a dirty book you shouldn’t read. Now let me show you why, page by page, you should not touch this book.”

The gushing Mr. Ulin was implying that while none of the ghastly accusations may be true, you, dear reader, should know about them because they will titillate you.

A bad guy always gives himself away, doesn’t he?

In the penultimate paragraph, Mr. Ulin thrust into the reader’s face his membership card in the Angry Left. His unsupressible bias should have disqualified him from pretending he was doing a review. Instead, it was an excuse for another far left rant against the still regularly abused Ms. Palin.

Disingenuously, Mr. Ulin wrote:

“I have no doubt that McGinniss’ view of Palin is accurate: that she is narcissistic, undisciplined and unqualified for public life.”

To validate his screed, the angry Mr. Ulin added, “Still, I want more than innuendo to make the point.”

This is a lie.

Why, then, did Mr. Ulin write this undisguised, unprovoked attack?

As an Angry Left’er, the estimable Mr. Ulin — desperate as the McGinniss chap — needed a vehicle, just in case she runs, to tell you how much he loathes her.

Thanks, pal.