YOU DON'T have to be Irish to enjoy New York's St. Patrick's Day parade. Tens of thousands march, and millions enjoy the bands and bagpipes. An occasional "England Get Out of Ireland" sign appears, but by and large the parade has been an ethnic rather than a political celebration--a way for Irish-Americans to celebrate their roots, their survival and their success in the New World.

The organizers, the Ancient Order of Hibernians, usually name a prominent Irish American as honorary grand marshal. Last year they caused some discomfort by honoring Bobby Sands, the first of the Irish Republican Army hunger strikers to die. The IRA is an illegal terrorist organization that seeks to end British rule in Northern Ireland. This year the discomfort has turned to outrage, for the Hibernians have named Michael Flannery, a self-confessed IRA partisan and fund raiser. Recently he was tried, and acquitted, on a charge of conspiracy to supply arms to the IRA. At that trial he supported both the killing of British soldiers in Northern Ireland and the terrorist bombings of civilians in London. "They should get a touch of it themselves," he suggested.

The IRA killers and their henchmen are no band of leprechauns. It is ridiculous to look for a twinkle in the eye of a man who has raised money "for widows and orphans" and at the same time admits to supplying funds to terrorists who turn more innocent victims into widows and orphans. There is plenty of violence in Northern Ireland, on both sides. But it is worse than naive to support those who have a stake in preventing a peaceful solution, and it is outrageous to try to legitimize thugs by honoring their champion.

The Irish Embassy has condemned the choice. Sen. Daniel Patrick Moynihan and former Gov. Hugh Carey have announced they will boycott the parade. Cardinal Terence Cooke issued a statement lamenting the choice, but he has yet to announce whether he will attend. Unaccountably, other New York politicians, including Gov. Cuomo, Sen. D'Amato and Mayor Koch, seem to believe they should attend to show their respect for their Irish American constituents.

If enough Irish Americans express their indignation at the selection of Michael Flannery, their fellow citizens might understand better the feelings of most of those whose ancestors came from Ireland. If enough bystanders turn their backs on Mr. Flannery as he struts up Fifth Avenue, perhaps he and his allies will begin to understand that terrorists have few friends here. And if a few responsible Irish American leaders sit down on March 18 and begin to think about what group has a just claim to set the tone for next year's parade, the event may survive as the kind of celebration that all can join and enjoy.