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More and more American businesses, including car rental companies and airlines, an insurance giant, and a major bank, are severing ties with the National Rifle Association in the face of torrents of criticism from customers on social media.

The backlash began on Thursday after the First National Bank of Omaha (FNBO), which has an NRA-branded Visa credit card, said in a statement that it had decided not to renew the contract.

Shortly afterward, other companies announced they would end their NRA membership discount programs.

The groundswell comes amid calls for tighter gun control after the shooting at a high school in Parkland, Florida, last week that claimed the lives of 17 people. Those calls have been rejected by the NRA, which instead has pointed the finger at school security, the mental health system and the FBI.

A spokesman for Visa said in a statement: "FNBO has informed us of its intention not to renew the NRA co-branded card program when its agreement with the NRA expires. We will support the issuer’s efforts to wind down the portfolio smoothly."

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A marketing website for the card was offline as of Friday. But a cached version of it said customers would "DEFEND FREEDOM with the NRA Visa Card" by helping fund NRA programs. The ad said it gave members $35 after their first transaction, "enough to reimburse your one-year NRA membership!"

A screenshot of the now-ended NRA Visa card owned by First National Bank of Omaha.

Survivors of the Parkland shooting and customers took to social media to demand that companies end any NRA-related programs.

David Hogg, a survivor of the Parkland massacre, tweeted his gratitude to companies who announced they were ending their partnerships, and, in a series of individual tweets, Hogg asked other companies to follow suit.

Some did. Among those cutting ties with the NRA were the car rental groups Enterprise, Hertz, Avis and Budget; the insurance giant MetLife; the software firm Symantec; and the Boston-based home security company SimpliSafe. Delta and United also said in statements Saturday that they will no longer offer travel discounts for the NRA. Each airline asked that related information be removed from the NRA website.

United is notifying the NRA that we will no longer offer a discounted rate to their annual meeting and we are asking that the NRA remove our information from their website. — United Airlines (@united) February 24, 2018

NYU marketing professor Scott Galloway said the companies are making a smart business move to protect their brand.

"The most valuable person in world of consumer business is an 18 year old. They have influence over what the rest of us believe is 'cool' and have a lifetime of discretionary spending ahead of them," Galloway told NBC News. "Their recent galvanization against the issue has made the NRA very uncool and an easy target for firms wanting to say to the most important cohort 'Hey, we get it, and are with you.'"

But Matt Schulz, senior industry analyst at CreditCards.com, said that the firms are walking a thin line.

"This is a bold move," said Schulz in an email, "but also a risky one because passions burn so hot on both sides of the topic of guns. Many will applaud the move, but NRA members are famously loyal and the organization has shown itself as being very good at mobilizing its members, so there's a real possibility of a significant backlash."

Flags fly over a First National Bank branch in Omaha, Nebraska, on Feb. 23, 2018. The Nebraska-based First National Bank of Omaha said Thursday they will not renew its contract to issue the group's National Rifle Association Visa Card. Nati Harnik / AP

Amid the genuine customer and user outrage, it appeared that Russian trolls might be taking part in the campaign as well. Accounts with suspicious profiles that matched signs flagged by researchers as being likely trolls or bots tweeted about and directly at the individual companies. Some of the accounts taking aggressive stances also used hashtags flagged by Hamilton 68, which tracks activity by known Kremlin-linked accounts, and showed signs of automated behavior.

Suspicious Twitter accounts also jumped into the social media debate in the immediate aftermath of the shooting to stoke divides on both sides of the gun control debate and spread hoaxes.

The NRA said in a statement on Saturday that the companies' decision unfairly punishes its law-abiding members, and called the moves "a shameful display of political and civic cowardice" and predicted they would be replaced by other companies.

"The loss of a discount will neither scare nor distract one single NRA member from our mission to stand and defend the individual freedoms that have always made America the greatest nation in the world," the NRA said.