This tells you everything you need to know about the Giants' defense last night: Joe Theismann scored standing up. Tippy-toeing seven yards, the Redskins' irrepressible Captain Buddy -- "Perrier, I call him," a teammate once said -- took on New York safetyman Ernie Jones at the goal line. A head fake later, Theismann shook off Jones' loving embrace. TD. And Captain Buddy popped his cork in celebration, slamming the football to the turf triumphantly, as if he'd just done something grand.

The Bee Gees could have scored against New York last night. These weren't the New York Giants, they were the Gotham Gripers. By silly penalty, they gave the Redskins a touchdown when they had earned nothing but a missed 25-yard field goal. By the time it was 24-0, the Redskins had nearly as many first downs by penalty (four) as they did by running (five).

As bad as the Giants are -- and how good can any team be when it is giving up 25 points a week and having its quarterback sacked seven times a week? -- the Redskins haven't been much better, subjecting their faithful to the disconcerting habit of grabbing a big lead and then frittering it away. They had outscored the opposition by only a point, 54-53, and no one came to the Monday Night Festival at RFK with anything but fond hopes.

"If Rabbits Can Be Beaten, Giants Can Be, Too," a stadium banner said. The last time the Redskins were live in front of Humble Howard and the Giffer, Jimmy Carter was a big man in town. That was Oct. 2 last year, a day they remember in Cairo and Jerusalem for the Camp David accords; at RFK, it was the night the Redskins beat the Cowboys to go 5-0 with the president in the crowd.

Nothing much good has happened since for the Redskins or the president, one reduced to building for a future that is a long way off, the other who makes his news now in conjunction with killer bunnies, teasing senators and footraces to exhaustion. What Jimmy Carter needs, clearly, is the New York Giants for an opponent.

The poor Giants. They even called a timeout once on defense early in the third quarter. For what, no one knows. Poor Joe Pisarcik, the quarterback, had no protection from his offensive line against a Redskins' defensive line old enough (29, 34, 35, 36) to qualify for football Medicare. That Pisarcik even breathes today is tribute to man's indomitability.

All this is not to belittle the Redskins' accomplishment last night. History reminds us they have not always beaten the Giants. In fact, before winning an overtime game last season, they had lost four straight to the Giants, losing with George Allen as coach, losing with Billy Kilmer as quarterback, even with Richard Nixon as president.

And some of Joe Theismann's worst times have come against the heroes of his New Jersey boyhood. With all the interceptions Theismann threw, you'd have thought he dreamed of playing for the Giants so much that he just naturally threw to the guys in blue jerseys.

Not last night. "Theismann has arrived," his old teammate, Chris Hanburger, declared on television this week.

Theismann completed 18 of 28 passes last night for 153 yards and a touchdown. If it were small cause for riotous celebration when Captain Bubbly evaded the wishy-washy safetyman at the goal line, it nevertheless was important for Theismann -- for more than one reason.

The most obvious, of course, is that Theismann finally beat the Giants. Some of the painful, perhaps inhibiting, memories can be set aside.

More important, and perhaps reason for dancing into the night, was that the Redskins, from the seven-yard line, were bold enough to call a most unorthodox play -- a quarterback draw on third-and-goal.

To the naked eye, the play seemed another Theismann pass shaping up. But he kept the ball. He ran. Not in a circle. Not backwards. Not to no avail. Perrier bubbled nicely. Straight ahead to the end zone. And maybe that's why Theismann slammed the football down so strongly.

Certainly, a shutout of the Giants, who averaged only 206 yards a game in their first two losses, is a nicer thing by far than losing to the Giants. But it is a different thing by far than shutting out a real team. The 54,672 customers at RFK last night realized that, for they spiced their restrained enthusiasm with an occasional boo over an obvious failing.

Even when it was 17-0 at halftime, only zealots boasted. A beautiful lead? A signal of domination by superior forces? You might as well ask if Jimmy Carter is going to race a rabbit 6.2 miles at Hyannisport next week. That 17-0 lead was a mirage built more on the Giants' ineptitude than on the offensive abilities of the Redskins.

The first touchdown came when Karl Lorch a defensive end, touched a football for perhaps the first time in his professional life. Pisarcik tried to loft a pass over Lorch. With his customary accuracy, Pisarcik threw the pass about nose high. Lorch intercepted it and outran Pisarcik 31 yards to make it 10-0.

An 80-yard drive that put the Redskins ahead, 17-0, was more a gift than an earned reward. Twice the Giants committed penalties that gave the Redskins first downs, once running into the kicker to lose the ball.

A third penalty directly cost the Giants seven points. With time running out, Mark Moseley, the Redskins' generally infallible placekicker, missed a 25-yard field goal badly. But the Giants, terrible examples of discipline, were called for running into Moseley, too.

Given another chance, Theismann made the most of it. On the next play, with 13 seconds left in the half, Theismann passed to Clarence Harmon for a touchdown. No Giant was within five yards.

A Giant linebacker, Brian Kelley, watched in disgust and then asked two teammates what happened. Everybody shrugged.