We have been prepared to swallow a hell of a lot for the sake of peace. But every so often, something comes along that sticks in the craw so badly that it cannot be forced down.
It's an almost visceral reaction: you get to the point where you just cannot stomach one more instance of callous, self-righteous complacency, or one more blast of brazen disregard for the principles of honesty, truth and natural justice.
And that's the point that many of us have reached when it comes to ex-combatants serving as special advisers. Unelected, unaccountable former terrorists, sitting on fat salaries and occupying positions of great power at public expense, is wrong. And it's time we all stood up and said so.
There must be no fudge, no equivocation, no qualifying statements. This is not about employment rights, or ex-prisoners' rights.
It's not about the SDLP tying itself up in complicated knots over whether to block Jim Allister's Special Advisers Bill, which seeks to prevent people who have served extended time for serious criminal offences from being appointed to publicly funded posts.
In choosing to stand with victims rather than with Sinn Fein, the SDLP has – belatedly – done the right thing. But the greater issue at stake is our moral status as a society.
Do we want to reach the point where we can no longer comfortably look ourselves in the eye?
How much of our own fundamental integrity, our baseline decency, are we prepared to sacrifice in the interests of maintaining the current dysfunctional status quo?
If we're prepared to tolerate bombers, like Paul Kavanagh, on school boards of governors, or unelected killers, like Mary McArdle, stalking the corridors of power, where do we go from there?
What is most frightening is the prevailing moral lassitude over these issues. There is a kind of lazy, bloated indifference at work, which really couldn't give a stuff over what calibre of people we're paying to run this country.
(Because, make no mistake, these mysterious special advisers aren't sitting up at Stormont twiddling their thumbs. They are remarkably powerful, influential figures who answer to no-one but the minister who appointed them; loyal sidekicks working for the party interest at public expense, who are fully capable of riding roughshod over anyone who gets in their way.)
It appears that our moral compasses – always a bit unreliable in this part of the world – have become so warped, rusted and distorted by lack of use that they are simply not fit for purpose anymore.
The Good Friday Agreement taught us to put pragmatism ahead of principle and we learned that lesson so obediently and so well that it seems we're no longer capable of distinguishing between right and wrong, only between winning and losing.
Willingly, or unwillingly, we have embraced our identity as an aberrant statelet, where the everyday human values of compassion and respect need not apply, or can be trumped by the more pressing needs of the all-consuming 'peace process'.
We are a special case, a special exception. As a result, political ethics in this country amounts to no more than a tawdry game of mean-minded point-scoring, bogged down in the boorish hucksterism which has long defined this place.
Certain republican-leaning commentators have claimed that the Special Advisers Bill is part of that same point-scoring punitive agenda, concerned only with the vindictive desire for retribution. There may be some truth in that.
Whatever the original motivation behind it, however, the Bill at least serves as a symbolic rallying-point for those who have no desire to seek punishment, or vengeance, but who are sickened by the steady erosion of basic ethical standards, and the thinly-veiled contempt with which victims are often treated.
Yet it would be a mistake to regard the issue of ex-prisoner Spads as one of concern only to those physically, or mentally, injured by the conflict. This is not about what is right or wrong for victims, important though their frequently overlooked and diverse needs should be. It is about what is right or wrong for all of us.
There is a moral deficit at work here, which shows itself not only in ethically questionable public appointments, but in the high-handed, autocratic and furtive way that the very business of government is carried out, in careless defiance of accountability and transparency.
That's why it's so vital that we establish these ethical bottom lines, beyond which we are not prepared to go.
Because, if we don't, there's no telling how far – and how fast – we will fall.