Rejection of gay marriage divorces us from rest of UK
On a visit to Ireland, he explained to journalists how devolved government worked in his country. "Sometimes, I'm a Bostonian,'' O'Neill said. "Then I do what I want. Other times, I'm an American. Then I do what I'm told.''
O'Neill's simple philosophy ensured a good working relationship with presidents who sometimes held very different views from his own and who often advanced policies that did not have the support of a majority of voters in Massachusetts.
It is a philosophy that our legislators at Stormont should think about as they ponder their tactics in the debate on gay marriage.
They should bear it in mind before heading down a road that is not approved by Westminster on a route not taken by the rest of the United Kingdom.
The boundary between local and national democracy is not clearly defined, but we all know roughly where it falls.
A town council can close its parks whenever it wants, but it can't cut the rate of income tax. A regional parliament can change the traffic laws, but it can't introduce the death penalty.
It doesn't matter if most of the townsfolk favour lower taxes, or a clear majority of the region's voters want to bring back hanging. These issues are the rightful prerogative of national government.
When they are up for decision, the only majority that counts is the national one.
In spite of the threats and prophesies of doom, the Same-Sex Couples Bill has cleared the Commons and is trundling its way towards the Lords.
Their lordships will huff and puff, but they will not bring down the house around their heads. The Bill will be law in England and Wales by autumn and Scotland will follow suit.
But, if unionist ministers have their way, Northern Ireland will not implement important parts of the new law. They do not want to legalise same-sex marriages here and will treat such British marriages only as civil partnerships.
Same-sex couples will not be allowed to adopt a child here, either as partners, or as individuals.
Two lawyers – Professor Brice Dickson, from the Human Rights Centre at Queen's University, and Rosemary Craig, a family law expert from the University of Ulster – have warned that this approach could create a legal minefield and a string of test cases. "These proposals could swamp our family courts,'' warned Ms Craig.
They are right to sound the warning, although it hardly needs a lawyer to point out the pitfalls.
What would be the status of same-sex couples who are married in Britain and then move to Northern Ireland? What of their adopted children?
And what would be the legal standing of same-sex couples from Northern Ireland who go to Britain to be married?
A way might be found around these problems, for we are good at fudging and turning a blind eye when it suits us.
But behind them lies a more fundamental issue that goes to the very heart of Northern Ireland's status within the UK.
There are times when regionalism cannot be allowed to triumph over a national vote and this is surely one of them. You cannot be married in one part of a country and not in another part.
Opting out of a country's marriage laws is as fundamental as opting out of its currency, or refusing to recognise its head of state.
Yet it is the unionist parties – the parties that most prize Northern Ireland's position within the UK – who are pushing us down this road.
When Belfast City Council voted in support of gay marriage last year, most unionists left the chamber and they were almost unanimous in their rejection of the development when it was considered by the Assembly in April.
When the Same-Sex Couples Bill came before the Commons earlier this month, the DUP members present all voted against.
All of that is their right and entitlement – to argue against a measure that does not meet with their approval. Like Tip O'Neill, when being a Bostonian, they can do what they want, or what they perceive their voters to want.
But when Tip was being an American, he did what he was told. When unionists are being British, they should follow the same principle.
Sammy Wilson, whose department is responsible for family law, has forwarded to his Executive colleagues a document known as a Legislative Consent Motion, which would permit the marriage legislation to be extended to Northern Ireland, but with key opt-outs.
He should think again. Acceptance of the law does not imply approval, but simply an understanding of where the authority of a regional parliament ends and the prerogative of a national parliament extends.
Rejection will undermine Northern Ireland's Britishness more seriously than the withdrawal of a Union flag, or any such gesture.