A PLAQUE at Chick-fil-A’s headquarters in Atlanta says the company’s mission is to “glorify God”, which it does by serving chickenburgers and closing its 1,600 outlets on Sundays. The founder, Truett Cathy, once said that while “you don’t have to be a Christian to work at Chick-fil-A…we ask you to base your business on Biblical principles because they work.”

His son Dan, the fast-food chain’s current boss, is also devout, so it should have surprised no one when he told a Christian news organisation that he disapproved of gay marriage. Yet the reaction was swift and strident. Gay-rights groups called for protests and boycotts (see picture). On August 3rd gay couples planned to stage a “kiss-in” at selected Chick-fil-A outlets. The mayors of Chicago, Boston and San Francisco all declared Chick-fil-A unwelcome in their cities—not because the firm refuses to hire or serve gays, but because its boss expressed an opinion that irks them.

Such dust-ups are not common, but they can hurt a business badly. Chick-fil-A could sue if a city actually blocked a restaurant because of its boss’s religious views. But customers can boycott a restaurant for any reason they please. So here are The Economist’s tips on how companies can avoid causing offence.

First, don't discuss religion in public. Few people will buy your margarine just because you are Zoroastrian. Plenty may shun it if you loudly espouse dogma they find disagreeable. This tip applies doubly to global firms, which must serve customers of every faith and none.

Second, if you must discuss religion in public, keep it bland and woolly. Zhang Xin, one of China's biggest property developers, is a devoted Baha'i. However, when she frets aloud about whether her country has lost its moral moorings, she does so in non-religious, or at most broadly spiritual, language. Such circumspection is the norm for public figures in China. The Chinese government is deeply suspicious of religion and professions of faith are not a regular part of public discourse.