A world-renowned travel guide has compared murals in unionist areas as comic-book like while those in the republican areas are "Sistine Chapel-lite".
The comparison was made in Fodor's Travel website and used by Singapore Airlines in their travel guide, the BBC reported.
On loyalist murals, the guide said they had taken on a "grimmer air".
"Typical subjects include wall-eyed paramilitaries perpetually standing firm against increasing liberalism, nationalism and all the other -isms Protestants see eroding their stern, Bible-driven way of life," the guide said.
Republican artwork, however, featured "themes of freedom from oppression, and a rising nationalist confidence that romantically and surreally mix and match images from the Book Of Kells, the Celtic mist mock-heroic posters of the Irish artist Jim Fitzpatrick, assorted phoenixes rising from the ashes and revolutionaries clad in splendidly idiosyncratic sombreros and bandanas from ideological battlegrounds in Mexico and South America".
Fodor's said it would remove the content and Singapore Airlines which used the company's material has begun a review.
Professor Peter Shirlow, head of Irish Studies at Liverpool University, said he was shocked by the content.
"It is something which plays on many sectarian myths we have in our society," he said.
"It represented the Protestant community as humourless, it represented them as Bible bashers, against liberalism and it evoked an idea that on the other side there was humour, a capacity for art and also evoked the idea republican violence was something to be glorified and where it represented the unionist community, it is not.
"If it was the Catholic, nationalist, republican community [being lampooned] I would say the same thing. It is just ultimately wrong and gave an incredibly unfair representation of murals in the city.
He said there were issues which needed to be addressed in terms of tourism and how the story of Northern Ireland was told to visitors. He said he had been on tours of the city and heard a "glorification" of one side and a "complete disregard for the suffering and harm caused to another side".
"Thousands come to the city because of the murals," he said, "there has to be some way we measure and ensure balance."
Fodor's Travel said the content had been removed from its website and would be taken out of ebooks and from its print editions.
"Fodor's Travel is always listening to the feedback we receive about our content, and we take action when we're notified of content that is outdated, inaccurate, or insensitive by updating and/or removing that content," it said in a statement.
Singapore Airlines said the content was provided by Fodor's and it would review the matter.