The tipping-point was the disgusting and yobbish behaviour by certain Celtic fans at Fir Park last Friday night. To see the way seats were kicked-in in that stadium, and the grim photographic evidence afterwards, was one of the greatest humiliations heaped on Celtic in years.
Doubts remain as to whether they were specific Green Brigade members, but the miscreants were within their space, behind their banners, and to all intents were a part of a noisy Green Brigade presence.
Peter Lawwell, the Celtic CEO, is now thoroughly exasperated. He has forthwith banned 128 Celtic supporters from matches and is now dispersing Section 111, the corner of Celtic Park where the Green Brigade have stood since 2006.
This has been a complex saga from the start. Not everything about the Green Brigade has been bad for Celtic. Indeed, some of their antics up in the stands have been impressive and to be admired.
Their booming "Come On You Bhoys In Green", which reverberates around the stadium like a tribal African chant, being picked up by fellow supporters in all corners of the ground, was something to behold.
More than once in the past Neil Lennon, the Celtic manager, has marvelled at brilliant acoustics of the Green Brigade's singing.
But there was more than this to their repertoire. In particular, the Irish political struggle, which has deposited much of its baggage in the west of Scotland in recent decades, appeared to be an essential of the Green Brigade handbook.
For many Green Brigade members it often seemed that, just as mandatory as actually supporting Celtic, was adhering to a devotion for Bobby Sands, the IRA hunger-striker. The Green Brigade's political chanting in favour of Irish Republicanism was nowhere near as frequent as some made out but, when it did rise up, it was enough to exasperate a majority of Celtic supporters.
In this context Celtic as a club, let alone the Scottish Parliament, has never quite been able to square the circle. Celtic's Irish roots deserve to be cherished, as do the roots of any family or football club.
In Celtic's case, these roots stem from Ireland, and a pitiful saga of over 140 years ago. And it is a saga that has witnessed pain and dispute in almost every decade since then.
In short, these are incendiary roots to cherish, roots which are fraught with danger and bound to divide and offend. In this context there are two distinct narratives (in fact more than two) - one offered in Britain and one offered in Ireland - and both aspire to be "the truth" about the Irish struggle.
With a group like the Green Brigade, Celtic FC has become mired in this. Theirs is a dangerous history and here in 2013 it has proved impossible to keep it inoffensive. The Green Brigade have seen to it.
The vast majority of Celtic fans take a distinctly different tack. There is no rampant Irish political expression among them. They cannot be bothered, frankly, with Bobby Sands.
The reason for this is pretty simple: the Celtic support is a variegated leaf, comprised of obvious Irish/Catholic roots, but also with a healthy Protestant element among it, as well as other ethnic groups.
By its sheer variety, the wider Celtic fanbase has a more watery view of the relevance of Ireland, as witnessed by a less than sympathetic ear extended towards the Green Brigade's plight of the past 24 hours.
In short, the Green Brigade's booming anthems have been much-admired; had they contained themselves to these they would have remained much-loved around Parkhead. But their political polemic - centred often on Sands and the IRA - has left most fellow-Celtic fans cold.
Celtic are now going through something similar to the trials of Rangers and their supporters' troubles of recent years.
The Ibrox club wrestled for decades with a problem of bigoted singing among its supporters, resulting in various pleas from the Ibrox hierarchy over many years for it to cease.
In 2006, when Uefa censured Rangers over such singing, it left a stigma on the club which Rangers toiled to shake off. The truth is, many Celtic fans revelled in this public embarrassment of their great rivals.
Now Celtic are receiving a dose of it, and have been publicly embarrassed. In disbanding the Green Brigade, the club hopes to finally be rid of unwanted attention.
As Rangers have already shown, though, it might take years and years in the cleansing.