“Going to Africa. Hope I don’t get AIDS. Just kidding. I’m white!” And just like that one woman’s callousness and casual racism became the Internet’s evening entertainment.

Public relations professional Justine Sacco probably didn’t think much of the tweet as she sent it from London’s Heathrow Airport shortly before boarding a 9-hour flight to South Africa. But as the director of communications for a billion-dollar media company, one Sacco listed in her Twitter bio, she probably should have. It’s pretty indefensible.

Like many people watching the spectacle unfold online, I was disgusted and angry at first. Then I imagined Sacco’s phone coming out of airplane mode and giggled my a** off.

The tweet set off a firestorm. According to Twitter analytic tool Topsy, Justine Sacco’s now deleted account garnered more than 45,000 tweets in the past 24 hours. Twitter user @shortstack81wondered #HasJustineLandedYet just 30 minutes into her flight. In the time it took to fly from London to South Africa, the hashtag was nearly 56,000 tweets strong and Sacco’s employer had scrubbed their site clean of any trace she’d ever been on payroll.

As with #PaulasBestDishes, #RacismEndedWhen and #USATodayBreakingNews, Black Twitter had struck a resounding blow with usual biting humor.

“Sometimes you land with more baggage than you took off with,” mused @monteiro. @twice_sifted tweeted, “If she is traveling with the company credit card, that first attempt at swiping is going to be a rude awakening.” It was all brilliantly capped with the purchase of JustineSacco.com, which was redirected to Aid for Africa’s donation page. Not everyone was amused.

“It was hard to ignore a disturbing feeling in the mob’s response, and something creepy in the trial by social media that was going on in her absence,” wrote Chris Taylor, Mashable’s deputy editor. “There’s a fine line between slamming Sacco for her blatant what-guys-I-was-just-kidding buffoonery, and taking an unconscionable delight in the misfortune of others while playing Big Brother on their lives.”

Unconscionable? Misfortune?

It has been estimated that more than 75 million people worldwide have contracted HIV/AIDS since the illness was first identified, and over 36 million have died from an HIV-related cause. And it’s a sad truth that many of the dead were poor people of color on the continent of Africa.

In fact, 75 percent of the HIV/AIDS-related deaths in 2012 were of people living in Sub-Saharan Africa. That Sacco’s career in PR was likely ended with the same ease she could work this tragedy into a “joke” is more than schadenfreude, as Taylor suggests.

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Waiting for Justine Sacco’s flight to land was like watching Wile E. Coyote chase The Road Runner off a cliff only to realize too late that that he’d run out of ground. Seeing her delete the tweet then her entire Twitter account was like watching gravity work. It felt something like justice.

Now, of course, flooding Sacco’s Twitter mentions didn’t end racism, xenophobia and general nastiness. But what it did do — more than likely — was end her career in corporate communications and that means something in a society where people of color put up with racism on a scale from micro-aggression to full-out slur everyday.

Hopefully, Sacco’s shaming will serve as an example to other casual racists that people of color are tired of being the butt of their “jokes,” that there are limitations to privilege, words matter and that those of us with good sense are willing to teach them those lesson one Sacco, USA Today and Paula Deen at a time.

Donovan X. Ramsey is a multimedia journalist who writes about all things social, political, cultural, financial and whimsical. Follow him on Facebook and Twitter @iDXR, or DonovanXRamsey.com.