The most fascinating part of White House press secretary Sean Spicer's first official briefing Monday was his explanation of why President Trump seems so thin-skinned at times.

Asked why Trump fixates on things like his inauguration crowd size, which Spicer defended using false claims Saturday, Spicer responded with an eight-minute, impassioned defense.

Spicer said that it was basically a defense mechanism — a reaction to the media's relentless negative coverage of Trump. Spicer used the word “demoralizing” no fewer than three times.

Here's a condensed version:

It's not just about a crowd size. It's about this constant — you know, 'He's not going to run.' Then 'If he runs, he's going to drop out'. Then, 'If he runs, he can't win,' 'There's no way he can win Pennsylvania,' 'There's no way he can win Michigan.' There is this constant theme to undercut the enormous support that he has. And I think that it's just unbelievably frustrating when you're continually told it's not big enough, it's not good enough, you can't win.
He's gone out there and defied the odds over and over and over again. And he keeps getting told what he can't do by this narrative that's out there. And he exceeds it every single time. And I think there's an overall frustration when you — when you turn on the television over and over again and get told that there's this narrative that you didn't win. You weren't going to run. You can't pick up this state.
And then to hear, 'Well, look at this [camera] shot,' and it's not — 'It wasn't that big.' It's a little demoralizing, because when you're sitting there and you're looking out and you're in awe of just how awesome that view is and how many people are there and you go back and you turn on the television and you see shots of comparing this and that. And then you look at the stuff that's happening.

Spicer added: “The default narrative is always negative, and it's demoralizing.”

Now contrast this with what happened later Monday. During a meeting with congressional leaders, Trump's defense mechanism kicked in again. While reliving the 2016 election, Trump again excused his popular-vote loss using the widely disproved and baseless conspiracy theory that millions of people voted illegally. Trump pegged the number at between 3 million and 5 million — as much as 3.6 percent of all votes cast.

I'm not going to dwell here on how utterly unfounded this claim is (The Post's Fact Checker has you covered on that one). Suffice it to say, the idea of having to write about this again is demoralizing.

Spicer is right that the vast majority of Trump coverage could be construed as negative. A post-election study from Harvard's Shorenstein Center on Media, Politics and Public Policy, in fact, found that 77 percent of it was negative. And it's an inescapable fact that members of the media tend to be more liberal and need to be aware of their personal biases.

But the juxtaposition of the two events Monday couldn't be clearer. Here, on the one had, was Spicer wondering why the media was so relentlessly negative about his boss. And not only was he saying this in response to his own faulty facts; he said it just hours before Trump re-purposed one of his most harebrained conspiracy theories about the 2016 election — a claim that, were it based in reality, would be a massive scandal.

The fact is that Trump begs for this kind of coverage. He's either addicted to controversy or extremely bad at avoiding it. The reason he gets coverage that could be construed as negative is because he does so many objectively controversial things, engages in so many feuds and makes regular claims without merit that are easily disproved. As our own Chris Cillizza so aptly put it, it's “sort of like being surprised that you attract bears after you smeared yourself with honey in the middle of the forest. Actions have consequences.”

The media loves controversy, because it involves conflict and a debate about what's right and wrong. And it doesn't have to reach for controversial things to write about Trump; he provides them on an almost daily basis. So when he and Spicer go out there and say things that are just wrong, the later professions of surprise and exasperation at the resulting coverage are too cute by half.

This is also the case with the initial media coverage of Trump's inauguration crowd. The reason the media focused on Trump's inaugural crowd size is about 90 percent Trump's own doing. He made various claims about how big his inauguration would be in the days and weeks before, including the laughable claim that dresses were selling out in the D.C. area. And he regularly accused the media during his campaign of not focusing enough on his crowd sizes when they were “yuge.”

Given that buildup, how could we ignore how unspectacular the crowd was at his inauguration?

It's one thing to lash out at negative media coverage and fight back against those who are minimizing your success by pointing to logical arguments. Point out that your base isn't on the East Coast and might not be able to make the travel arrangements work. That's a fair argument. Point out that the white ground coverings may have made the crowd look sparser than it was. That's fair too. Even Spicer's comment about the media underselling Trump's chances of winning is totally fair criticism.

But it's another to respond with a bunch of made-up, fabulist claims that lead to the utterly predictable result of more — and justifiably so — negative coverage.

The solution for Trump here couldn't be more simple. But I doubt he wants to hear it, and given his treatment of people like Spicer, I doubt anyone's really trying to deliver him a reality check.