The link between sport and politics has a long and distinguished history.

From the 1936 Olympics in Berlin - when black, US athlete Jesse Owens gate-crashed Hitler’s plans for a propaganda showcase of Aryan domination - to the black-fisted salute of African American sprinters Tommie Smith and John Carlos during a medal ceremony at the Mexico City Games in 1968, sports men and women have played an important role in changing attitudes at crucial staging posts in that country’s civil rights movement.

Muhammed Ali surrendered his World Heavyweight boxing title rather than fight for his country’s "imperialist" war in Vietnam.

Billie Jean King fought, not just for equal pay for female tennis players, but for the rights of women generally.

Read more: Green Brigade urge Celtic fans to join Palestine flag display

Glenn Burke, the first Major League Baseball player to "come out" as gay in 1982; Carl Nassib, who did the same in the NFL in 2021; and Fallon Fox, the first openly transgender American mixed martial artist, have advanced the cause, not just of LGBTQ+ athletes, but of the push for LGBTQ+ equality generally.

Those who insist there is no place for politics in sport are either ignorant or complacent, or they have something to lose - usually money.

Politics is as much part of sport as it is business, the arts, civic society and international affairs, or anything else that involves so much finance, participation, and public attention.

How can it not be? Where issues of resourcing, access, propagandising, and the exercise of human rights are involved, sport inevitably follows. It’s not called sportswashing for nothing.

So, should the expected imposition of disciplinary action by Uefa, European football’s governing body , against Celtic FC, after a section of their supporters displayed hundreds of Palestinian flags during the team’s Champions League match against Atletico Madrid last week, be condemned and resisted? Were the fans not simply exercising their freedom of expression?

It comes after the club were fined €20,000 last month in response to the same section of fans, the so-called Green Brigade, displaying a "provocative" and "offensive" banner during an earlier tie against the Italian side, Lazio, which read ‘Antifascist Glasgow Celtic’.

UEFA, and its global counterpart FIFA, are hardly models of ethical and fiscal probity. Both have been mired in financial scandal in the past and are seen by many as retirement homes for well-fed, kickback junkies, lining their pockets on the proceeds of the global game.

But there is a difference between a player, or a club, taking a position, and a group of fans - whose behaviour reflects back on the club and the players - on an issue as politically and morally nuanced as the current bloodbath in the Middle East.

The club, which has now banned the Green Brigade from Celtic Park and all away games, has taken a resolutely neutral stand on the crisis, issuing a statement that said it was praying for peace and humanitarian support in the region.

"Against this backdrop of conflict and pain, sport can promote peace and demonstrate humanity and empathy for all who continue to suffer," the statement said.

Ultimately, however, the club are responsible for the behaviour of their fans, both in their own stadium and at away fixtures, and they have consistently failed to control the behaviour of the Green Brigade in the past.

For those who don’t know, the Green Brigade are a group comprising Celtic "ultras" - a term borrowed from followers of Italian teams, referring to the most passionate and fanatical supporters.

With numbers running into thousands, they are the most vocal and colourful fans, occupying the north curve corner of Celtic Park, and their creative, often humorous banners, which they unfurl at the start of games, are eagerly anticipated by the rest of the crowd.

But the Green Brigade are also a peculiarly secretive and shadowy organisation and, for one with such trenchant and provocative views,  they are conspicuously reluctant to reveal who their leading lights are.

Most members are young men, and yet their statements are sober and considered missives, voicing hardened political views.

In the past their banners have featured Bobby Sands, the IRA hunger striker, and they have protested against poppies being used on the club's strip. One said: "Your deeds would shame all the devils in Hell. Ireland, Iraq, Afghanistan. No Blood Stained Poppies on Our Hoops."

This all contributes to a suspicion that, while the excitable young men jumping up and down to rhythmic drumbeats at matches are the public face of the Green Brigade, their strings are being pulled from elsewhere.

The Palestinian flag is waved regularly in their corner of Celtic Park, as is the Basque flag, both representing causes where violence has been used as a means of seeking to settle political conflict.

But why not the Catalan flag or even the Saltire, both of which more accurately reflect the current desire in the wider Irish Republican movement to achieve independence through electoral means?

Ahead of distributing Palestinian flags to fans arriving at Celtic Park for the Atletico Madrid match, the Green Brigade leadership - whoever they might be - issued a statement urging fans to respect the right of all those who wished to participate in its action.

But what about the fans who do not wish to be tarred by association? In the current climate, the flying of the Palestinian flag might be seen to support the victims of Israel’s military incursion in Gaza or it might equally be seen as backing for Hamas, whose foot-soldiers brutally slaughtered more than 1,200 innocent Israelis, including elderly women and children, on October 11, in the biggest and most savage killing of Jews since the Holocaust. The Green Brigade have failed to declare which group their protest was directed at, nor to respect the club’s request not to fly the Palestinian flag at matches.

Read more: Why 'Pig Watch' and Palestine protest have put Celtic ultras on brink

Participation in politics includes knowing when to observe codes of decency and discretion and blunt, ill-conceived gestures such as theirs respect neither.

Celtic have a talented Israeli player on their books, Liel Abada, whose current injury precludes him from playing, and who is likely to leave for a new club during the next transfer window, in January.

If that transpires, and the behaviour of the Green Brigade is cited as a reason for his departure, Celtic will have to explain to the rest of their supporters, as well as to the outside world, why they have allowed it to happen.

The board and management may wish not to involve politics in the running of the club, but they had little choice.