Brawling soccer fans and the appearance of an anti-Catholic video are the latest incidents that show the ugly side of soccer is still alive in Scotland.

Soccer rivalries are famous in Europe, and none is more fierce than the one between Celtic F.C. and Rangers F.C. in Glasgow.

Although some rivalries can be friendly, the clashes of the “Old Firm” – the collective name for the two clubs – are anything but, mixing nationalism and religious sectarianism with sporting prowess.

Rangers is the Protestant club, while Celtic is the Catholic one – it was even founded by a priest. Although the teams ply their trade in the largest city of Scotland, it is Northern Ireland which dominates the culture of the clubs.

Scottish flags – which can be found almost everywhere in the country – are not common in the teams’ stadiums: Celtic fans fly the Irish tri-color, while Rangers fans fly the Union Jack or even the Northern Irish flag.

The latest clash was on April 29, shortly after Celtic beat Rangers 5-1 in the final meeting of the two teams in the season. At least one person was sent to the hospital.

Later that evening, a clip was downloaded onto the internet showing a group of men wearing Rangers jerseys, surrounded by Union Jacks and Northern Irish flags chanting: “Then you put your arms around and we stumble to the ground and we say we hate Catholics, everybody hates Roman Catholics.”

“Sectarianism is, alas, still present, despite attempts to quell it,” said Ronnie Convery, the Director of Communications for the Archdiocese of Glasgow.

“Things are not as bad as in the past, but it is not unusual to hear tens of thousands of voices singing that they’re ‘up to their knees in Fenian blood’ for example,” he told Crux.

The Fenians were a 19th century Irish nationalist organization, and the word is now a derogatory term for Catholics – implying they are members of the Irish Republican Army or other nationalist militant groups – in Britain and Northern Ireland.

“Similarly there will be chants about King William of Orange or references to the IRA or the UDA [Ulster Defense Association, a Protestant paramilitary group] in much of the crowd chanting,” Convery said. “The fixture is always heavily policed, fans are kept apart arriving and departing from the ground, and there is a spike in domestic abuse following the fixture, which is alarming.”

As late as the 1980’s, Rangers had an unofficial ban on Catholics playing for them.

When manager Graeme Souness signed Mo Johnston in 1989, he was the first Catholic to play for Rangers since at least World War I.

“The rivalry between Rangers and Celtic goes far beyond football – it’s religion, it’s politics, it’s both the savoury and unsavoury of the sport,” Souness wrote on the Sky Sports website on April 29.

“To be honest, the religious aspect was not something I ever really bought into,” he said. “I grew up in Edinburgh, and then I was in England, so it was never really a part of my life.”

Souness said the first question any manager of Rangers would be asked is: “Would you sign a Catholic?”

“Times were changing, it seemed, everywhere else but Glasgow. And it was time the city caught up,” he said.

Despite the manager’s enlightened attitude, the fans were not thrilled with the signing. Some burned their club scarves, or cancelled season tickets, and Johnston was often ostracized by other players and staff.

Catholics in the city called Johnston – who had previously played for Celtic – a traitor.

But his signing was a revolution for both clubs, according to Souness: “All of a sudden, instead of half of Scotland being looked at by Rangers or Celtic, all of them were.”

The fans, however, are still bitterly divided. Since Johnston’s signing, brawls and even riots still happen when the teams meet. In that time, several people have even been killed in football-related violence.

Convery told Crux religious leaders and politicians work together to make clear that sectarianism is socially unacceptable, “but often in the cauldron of the stadium, when the great rivals take to the park, the opposing fans behave very differently to their normal standards.”

He said it’s a problem which the police, schools and the media also try to highlight and resolve, “but the rivalry is extremely deep-rooted.”

The matter is not helped by the realities of Scottish soccer: In most leagues, teams meet twice a season in league play – home and away – and might possibly meet once more if they happen to draw one another in the national knock-out cup tournament.

But the Scottish league is smaller, and Rangers and Celtic will often meet each other four times a year in league play; and since they are the best teams, and almost always win, they usually meet each other in the two national cup tournaments. This means they could meet six times a year, which is a lot of opportunity for trouble.

In 2012, the city almost sighed with relief when Rangers went bankrupt, was reorganized, and forced into the lowest tier of professional Scottish soccer, meaning the Old Firm matches would be suspended until Rangers fought their way back into the Scottish Premiership.

The same year, Scotland passed the Offensive Behaviour at Football and Threatening Communications Act, which gave police more power to fight the sectarianism surrounding soccer matches.

The law has been being used more often this season, the first with Rangers back in the top division.

The violence – some Rangers fans even stormed the pitch during last weekend’s game – could be just because of pent up tension being released as the Old Firm went back into business.

But Convery insists this is a soccer problem, not a Scotland, or even a Glasgow, problem.

“Bigotry is not routinely visible in daily life,” he said. “There can be pockets of hidden prejudice even in professional life, examples of bias in viewing the world, but modern Scotland is largely a tolerant and cosmopolitan place.”