Adam M. Smith, in a frame from his anti-Chick-fil-A YouTube rant.

An executive at a medical manufacturing firm lost his job after a YouTube video of him verbally ambushing a young employee at a Tucson Chick-fil-A went viral.

Adam Smith, formerly Chief Financial Officer at Vante, stepped down after the video — which Smith shot and uploaded himself —caused embarrassment to the company.

The video was picked up by countless blogs. Before Smith took it off of YouTube, others had downloaded it and re-posted it. Both the escapade and its fallout filled Tucson-linked tweets.

Smith, who served as an adjunct lecturer at the University of Arizona last semester, filmed himself berating a drive-thru employee at Chick-fil-A, 3605 E. Broadway, Wednesday. Conservative firebrand Mike Huckabee dubbed that day “Chick-fil-A Appreciation Day” and encouraged customers to eat there to show support for the chain after President Dan Cathy drew controversy for saying the company supports efforts to block gay marriage.

In the video, which runs 2 minutes, 21 seconds, Smith enters the drive-thru, explaining that he’s ordered a free cup of water. Once the employee hands him his cup, he lambastes her employer, calling Chick-fil-A “a hateful corporation” and “a horrible corporation with horrible values” that “gives money to hate groups.”

Chick-fil-A restaurants have been a source of political uproar after Cathy’s statements against same-sex marriage.

Cathy made statements in June and July in support of the biblical definition of marriage. Gay-rights groups have called for a boycott of the Atlanta-based company, and city leaders in Boston and Chicago have said new franchises would not be welcome there.

Protests critical of Cathy’s statements are expected today.

In Smith’s video, the employee at the drive-through window, taken aback, tells Smith that she’s uncomfortable being filmed. Smith does not back off.

“I don’t know how you live with yourself and work here,” Smith says to the employee, before calling himself “totally heterosexual” and saying there’s “not a gay in me” and “I just can’t stand the hate.” He also says he’s “I’m a nice guy, by the way.”

After he’s done talking to her, he says he thinks he “just did something really good” and “I feel purposeful.”

Roger Vogel, Chairman, President and CEO of Vante, said the decision for Smith to step down was mutual. Vogel said he was “shocked” by the video, which he first discovered when people emailed him a link.

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“We obviously found it very disturbing,” Vogel said. “We respect everybody’s ability to share their opinions in the public square and we have a very diverse workforce with a diverse set of opinions. We expect employees to behave in a professional manner that’s commensurate with their positions, and discuss their opinions in a civil fashion. ... We thought what he did was inappropriate.”

Vogel said the company has no stance on the gay marriage issue but has always hade a “good relationship” with Chick-fil-A. He said the company will consider contacting the employee Smith ambushed in an attempt to mend fences.

Reached at Chick-fil-A, the employee declined comment. Smith did not respond to messages left via email or through the University of Arizona. UA spokespeople did not return messages asking whether or not Smith would continue to teach classes, although Smith’s profile was scrubbed from UA’s faculty listings Thursday.

According to his LinkedIn profile, Smith taught Valuation and Corporate Finance to MBA students last semester.

Before accepting the job at Vante, Smith worked for more than seven years at IBM, where he was Senior Finance Manager. Smith earned a business degree at the UA, graduating in 1999, as well as an MBA in 2007.