WE WISH to add our thanks today to the incomparable, unbelievable, irresponsible Washington Bullets. By beating the Seattle SuperSonics for the third time in nine days, they have brought to all of Washington - except for a handful of diehard expatriates from the Pacific Northwest - the joy of the city's first major professional sports championship in 3 1/2 decades.

For the past two months, the Bullets have been something special. During a set of playoffs that seemed endless, following a "regular" season that had also seemed endless, they were generous with glory, passing it around lavishly on different nights (or days) to Kevin Grevey or Elvin Hayes or Bobby Dandridge or Tom Henderson or Charles Johnson or Mitch Kupchak or Larry Wright or Greg Ballard - or Coach Dick Motta for his strategic moves. So it was fitting when, with only 12 seconds left, it was suddenly team captain Wesley Unseld's turn. Too short to play center in this league of giants (or so it is said) and too slow to play elsewhere.Unseld is the model of a hard-working, determined, quiet man who makes the best of what he has. His best (two free throws at a time when the Sonics were only 2 points short) was enough to lock up the title for the Bullets and Washington.

The Bullets, even before they became champions, were more than just a basketball team in this town. From owner Abe Pollin on down, most of them are involved in working with young people, helping ex-convicts, aiding the handicapped and being good citizens. In a city where the playgrounds are alive with would-be basketball stars and the streets are alive with attractions that can lead them astray, the Bullets are champions of a sort even when they don't win championships.

But the championship is a gift of particular value to a diverse, often divided community with not all that many recent triumphs to celebrate. The Red-skins gave us that special glow of togetherness when they began to win in the early 1970s. And the Bullets have done it now. For the last couple of weeks, they have been giving cab drivers and politicians, bankers and government workers, and suburban and inner-city youths something nice to share. In a sprawling metropolitan area where there is so little sense of connection - Metro is almost the only other tie that binds - that is no small accomplishment. For more reasons than one, the Bullets have earned all the cheers they can get today.