Jeff Bezos speaking at the new New York Economic Club luncheon in New York on Oct. 27, 2016. Adam Jeffery | CNBC

Amazon took the rare step this week of responding to criticism from a politician, after Sen. Bernie Sanders went after what he called the company's poor working conditions. Amazon said the Vermont Democrat's claims were "inaccurate and misleading." Such swift denial has raised an important question for Amazon: What about Trump? The president has made Amazon a frequent punching bag on Twitter, targeting the company's tax payments, postal rates and CEO Jeff Bezos' ownership of the Washington Post, which Trump frequently bashes for how it covers him. Amazon has almost always remained silent, choosing not to trade barbs with Trump even when his statements have been provably false. So why take on Sanders? Given what's at stake for Amazon, the world's second most valuable company, and the potential future implications of Sanders' attacks on its business and brand, Amazon's decision to respond makes sense, according to public relations experts. "Amazon is making a calculated response based on what's best for their business," said Paul Argenti, a communications professor at Dartmouth College's Tuck School of Business.

More 'damaging' issue

The heart of Sanders' claim is that Amazon doesn't pay its lower-level employees a fair wage, while Bezos is the richest person in the world. It's an issue that all Americans can understand, particularly as the wealth gap between the haves and have-nots continues to widen. Trump's criticisms, by contrast, are more obscure and often don't make much sense, like when he said that Amazon was causing the post office to lose money or claimed that the Washington Post is protecting Amazon's ability to pay little in taxes. tweet "Americans are far more likely to care about images of poorly paid, mistreated workers, rather than fairly abstract taxation issues," said Dorie Clark, a branding expert and business professor at Duke University. Sanders is also perceived as a more credible critic, according to Steve Dishart, founder of Communications and Crisis Management Consultants. Trump has gained such a reputation for attacking companies with little to no evidence to support his claims that, in many instances, he's no longer taken seriously. "Trump's criticisms may have less bite than Sanders' since Trump attacks people and businesses at will and multiple times per day," Dishart said. Amazon investors certainly aren't deterred by the company's choice to ignore the president. In March, the stock dropped 4.4 percent on the day of a report in Axios, citing a source, that Trump was "obsessed with Amazon." But as Amazon remained silent, the stock price quickly recovered and has since jumped roughly 50 percent to a market cap that's approaching $1 trillion.

Engaging in a public feud with Sanders doesn't have the same potential impact, because the senator lacks the executive power to make sweeping changes that could hurt the company. "They can respond to him without worrying about share price," said Pallavi Kumar, a communications professor at American University. "But if they engage with Trump even one time, they will escalate into a Twitter war with no end in sight." Amazon didn't respond to a request for comment. There's another aspect of Sanders' remarks that touches a nerve inside Amazon. In addition to his concerns about low wages, which Sanders says are 9 percent below the industry average, and the company's lack of transparency when it comes to health and pay information of contractors in fulfillment centers, Sanders took aim at the working conditions in warehouses. Earlier this year, Bezos responded to similar criticisms in Germany, saying he was "very proud of our working conditions and I am very proud of the wages that we pay." It's not just fulfillment centers. Amazon's reputation took a hit in 2015 following a New York Times article that described a "bruising" work culture in many areas of the company.