Battle lines were drawn after its president, Dan Cathy, underscored his chain's opposition to same-sex marriage.
"Guilty as charged," Cathy told a Baptist news journal in North Carolina when asked about Chick-fil-A's multi-million-dollar financial support for groups that campaign against same-sex marriage.
"We are very much supportive of the family -- the biblical definition of the family unit. We are a family-owned business, a family-led business, and we are married to our first wives. We give God thanks for that."
In a subsequent radio interview, Cathy said the United States -- where President Barack Obama supports marriage equality, and his Republican rival Mitt Romney does not -- was "inviting God's judgment... when we shake a fist at Him" and legalize same-sex marriages.
God's judgment is still pending, but in the time it takes to serve up a Chick-fil-A Deluxe Chicken Sandwich with a side order of waffle potato fries, gay and lesbian rights activists and their allies were up in arms.
Boston Mayor Thomas Menino told Cathy in a letter that Chick-fil-A was not welcome in Beantown, as the New England city is known.
In Chicago, a city alderman moved to halt the building of a Chick-fil-A outlet in his ward.
The Jim Henson Company, creators of the wholesome "Sesame Street" puppets and birthplace of the Muppets franchise (now owned by Disney), said it would no longer supply toys or other merchandise to the chain.
In Washington on Thursday, about two dozen supporters of the Human Rights Campaign, a major gay civil rights group, targeted a Chick-fil-A food truck for a noon-hour protest.
"The Cathys have their personal beliefs, and that's fine," said protest spokesman Dan Rafter. "But there's a difference between personal beliefs and having them dictate your company's decisions and donations."
Harnessing social media, other LGBT activists have declared a "National Same-Sex Kiss Day" at all 1,600-plus Chick-fil-A locations on August 3, along with a consumer boycott.
But Chick-fil-A -- whose witty ad campaigns feature udderless Jersey cows encouraging humans to "Eat Mor Chikin" -- has its supporters, and it knows it.
Ranked the best fast-food chicken chain by Consumer Reports magazine, Chick-fil-A -- founded by Cathy's father in 1967 -- enjoyed revenues of $4.1 billion in 2011, up 13 percent from a year earlier.
"Hey Fans, thanks for being supportive," it said on its Facebook page, where it denied "100 percent" a bizarre claim that it had impersonated a teenager on the social networking site this week in order to defend itself.
Former Arkansas governor and 2008 presidential candidate turned talk show host Mike Huckabee appealed to Americans who favor traditional marriage to dine en masse at their local Chick-fil-A on August 1.
Billy Graham, the 93-year-old dean of Evangelist preachers, meanwhile praised the Cathy family's "public support for God's definition of marriage."
"As the son of a dairy farmer who milked many a cow, I plan to 'Eat Mor Chikin' and show my support by visiting Chick-fil-A next Wednesday," he said in a statement Thursday.
The National Organization for Marriage also endorsed August 1 as a chance to rally support for retaining the Defense of Marriage Act, which blocks the recognition of same-sex marriages at the federal level.
"Help us fight for traditional families and eat chicken at the same time," said former Pennsylvania senator and former White House hopeful Rick Santorum, who now runs a conservative advocacy group.
Same-sex marriage is recognized in eight states, including two -- Maryland and Washington -- where the concept will be put to referendums in November. It is banned by statute or state constitution in most other states.
Equality Matters, a gay rights group, citing public tax records, says Chick-fil-A and its charitable foundation WinShape has given millions of dollars to groups opposing same-sex marriage, including $1.9 million in 2010.
Waiting in line for their chicken lunches Thursday, patrons of a Chick-fil-A food truck in downtown Washington sympathized with the chain's critics -- but only up to a point.
"The issue isn't the restaurant," said lawyer Joe Esposito, 26, as he waited to place his order. "It isn't that there's discrimination in the restaurant -- that would be illegal and not acceptable."
Law firm employee Catie Butler, 21, agreed. "The food isn't anti-gay, just the owner," she said, describing Chick-fil-A's fare as "the best fast food there is."