Arizona Gov. Jan Brewer’s now famous photo-op with Barack Obama, in which she is seen pointing her finger at the president, has gone viral. And now, so has Brewer’s explanation.

According to Brewer, when she encountered President Obama on the tarmac at Phoenix-Mesa Gateway Airport on Wednesday, she gave him a handwritten letter inviting him to lunch and to survey the border, and instead, he dressed her down about parts of her book, Scorpions for Breakfast, in which she described a previous encounter with the president in the Oval Office in which he was, in her words, “condescending, professorial, and patronizing.”

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Brewer said she was taken aback. And she added:

“I felt a little bit threatened, if you will, in the attitude that he had, because I was there to welcome him,” she said.

Threatened?

Perhaps what Brewer meant was that she felt a bit threatened by the presence of Secret Service agents all around her as she thrust her finger into the president’s face. Or, perhaps she felt threatened at the prospect of the terrible publicity such an awkward photo op might produce…

Or, well you know, he is a rather tall and swarthy man (ahem).

Brewer’s faux pas can be read any number of ways. Not surprisingly, for African-Americans, it’s an unpleasant reminder of a stereotype that has dogged particularly black men for ages: that no matter how accomplished, or calm (and Obama is nothing if not both) they are, black men are “intimidating.” Brewer may not have meant it that way, but like the photo now seen ‘round the world, that’s how many will receive it.

The meme of the “threatening black man” has been around since the days of American slavery, and it persists to the point where studies have shown that white respondents tend to view the faces of black men as angry, even when they’re not.

For many black Americans, the fact that even President Obama is not exempt from the stereotype is galling, to say the least.

Not long after the quote went viral, New York Times columnist Charles Blow tweeted:

Brewer said she felt “a little bit threatened” by the President – CNN < Oh my. Was it his sagging pants or the way he was eyeing ur purse...

He later added:

I need to write a racist code word handbook for this election cycle. I think it would be a best-seller…

Meanwhile, the blogger New Black Woman wrote:

Sigh… really, Jan Brewer, threatened by a super, skinny intellectual black man serving as president of the United States? Nothing like the convenience of using the big, scary black man stereotype to excuse one’s racism and lack of deference to the person holding the highest office in the land…

Brewer’s encounter with the president was indicative of what supporters — and more than a few African-Americans — view as a general disrespect shown toward Barack Obama by some conservatives.

Actress Tichina Arnold tweeted:

Did Gov. Jan Brewer RUDELY put her finger in Pres. Obama’s Face?.. Yet another DISGRACEFUL moment 2ward the highest office in our land. Wow.

And social commentator and XM radio host Elon James White added this tweet:

Is there any pictures of Democrats waving their fingers in George Bush’s face? I’d love to see it…

It’s that disrespect, and the seeming stereotyping of a black man — even if he is the president of the United States — that makes Brewer’s unfortunate photo-op so toxic.

Follow Joy Reid on Twitter at @thereidreport