In the midst of the pandemic, a small piece of cloth has incited a nationwide feud about public health, civil liberties and personal freedom. Some Americans refuse to wear a facial covering out of principle. Others in this country are enraged by the way that people flout the mask mandates. Bob Palmgren tried to be polite - at first. He told a customer he had to wear a mask inside his restaurant, RJ's Bob-Be-Que Shack in Mission, Kansas. The customer, a man in his forties in a Make America Great Again (MAGA) cap, had flashed a gun and said that he was exempt from a state-wide mask requirement. He said that he could explain the exemption in the law to Mr Palmgren. Mr Palmgren, a former marine, told the customer that he was not interested in continuing the conversation. Mr Palmgren was not swayed by the customer's gun, either. "Coronavirus doesn't care if you have a gun or not," said Mr Palmgren, describing his conversation with the customer. "I said: 'Now get the hell out of here.'" The argument in the restaurant reflected a deep divide over requirements to wear masks in this country. People in Kansas, along with those who live in more than half of the country, are now required to wear masks in public as part of an ongoing effort to slow down the spread of the virus. But some people have been fighting against the mandate. The wearing of masks has become a catalyst for political conflict, an arena where scientific evidence is often viewed through a partisan lens. Most Democrats support the wearing of masks, according to a poll conducted by researchers at the Pew Research Center. Most Republicans do not. The Republicans are following the lead of the president: Trump has been reluctant to wear a mask, saying that it did not seem right to wear one while he was receiving heads of state at the White House. He put a mask on in public for the first time during a visit to a military hospital earlier this month. The battle over masks has escalated during the final weeks of the campaign season. The general election is in November, and activists in both parties, Republican and Democrat, are working feverishly to ensure victory at the polls. Some of them have faced off on the issue of masks: as Timothy Akers, a public-health professor at Morgan State University, a historically black college in Baltimore, says: "We're seeing politics and science literally crashing." The dispute over masks embodies the political dynamics of the campaign. It also reflects a classic American struggle between those who defend public safety and those who believe just as deeply in personal liberty. The conflict over masks is tense, volatile and deeply personal. Mr Palmgren, the owner of RJ's Bob-Be-Que Shack, was trying to follow the state mandate when he got into the argument with the gun-toting customer. Other stories about the masks have unfolded across the country. When workers in a Michigan pizzeria told a customer that she had to wear a mask, she made an obscene gesture, kicked someone in the restaurant and, according to local authorities, fled the police. A fight over masks led to gunfire outside a Los Angeles grocery store, according to authorities, and a rapper named Jerry Lewis was killed. The fight over masks is playing out against a backdrop of a health crisis that has reached historic levels. More than 3,544,000 people in the US have tested positive for the virus, according to the World Health Organization, and at least 137,000 people have died. The divide between those who wear masks and the anti-maskers, as they call themselves, has become increasingly sharp. In interviews in the Midwest and across the US, people dug in their heels and defended their position, whether for or against the wearing of masks. Many of those interviewed sounded deeply mistrustful of people on the other side and blamed them for the nation's economic and public-health crises. Resentment was palpable in the voice of Susan Wiles, a retired sign-language interpreter, as she described what happened to her at her local supermarket, Publix in Vero Beach, Florida. Mrs Wiles, who has an autoimmune disorder, was riding in a motorised cart in the produce department when a worker "jumped back", she says, and gave her "a glaring look". As she recalls: "He yelled: 'You're not wearing a mask.' It was quite a commotion. Another guy joined right in and said: 'She's a menace to society. Get her out of here.' Then he yells: 'Why don't you just go attend a Trump rally?'" As it happens, Mrs Wiles has been to the president's rallies. A Trump supporter, she says that she does not wear a mask because she believes that the concerns about Covid-19 are overblown. "Sure, there's a virus," she says. "But people die of the flu every year." When it comes to the pandemic, she says: "I don't fall for this. It's not what they say it is."