It is too bad Dave Parro was born in Canada. The way the goalie turned a crowd of Capital Centre malcontents into home-team loyalists last night would make him a natural for a presidential nomination in 1984.

It is also too bad Parro did not start the Capitals' game against the Stanley Cup champion New York Islanders. Although Parro blocked 21 of 22 shots during the last 49 1/2 minutes and inspired his teammates to their best effort of the season, an early 3-0 deficit was too much to overcome and the Islanders won, 4-2.

The teams move to Nassau Coliseum for an encore tonight (WDCA-TV-20 at 8) and it is a good bet that this time Parro will be in the starting lineup, as Washington tries to end a six-game losing streak.

Last night, Coach Gary Green removed Mike Palmateer after the Capitals' starter had yielded three goals in six shots.

No. 1 was scored by John Tonelli, after Palmateer came out to battle unguarded Bob Nystrom. No. 2 came from Mike Bossy, on a close-in drive that struck Palmateer's pad and trickled over the goal line. No. 3 was Tonelli's second of the game, as he converted a breakaway on which pursuing defenseman Terry Murray was reduced to spectator status.

Green watched the replay on the television set behind the bench, heard the boos from the stands and summoned Parro. The crowd of 11,706 then was treated to another replay, with different results.

Wayne Merrick broke free but this time defenseman Greg Theberge dived from behind to knock the puck away. Tonelli pounced on it, but a potential hat trick was averted as Parro made a fine save. He stopped two more from close range moments later, the fans began to chant "Par-ro, Par-ro" and the Capitals took the play to the other end.

Gaetan Duchesne's second goal of the season cut the deficit to 3-1 before the first period ended and Tim Tookey, playing despite a wrenched knee, made it 3-2 in the second. There were many opportunities for Washington to pull even, but it did not happen and Bossy finally wrapped it up by completing his fourth two-goal game of the season with 10:41 remaining.

The fans, most happy just to see the home team make a reasonable effort, were generous with their applause at the end of the second period and at the finish.

The Capitals, who outshot New York, 12-7, in the second period, could muster only four shots in the final 20 minutes as the Islanders turned to their clutch-and-grab tactics to protect the lead.

"They clutched, grabbed, held, hooked, anything possible," Green said. "They're a good, disciplined team and they got away with it. Our forwards had a tough time getting in there. They're big and strong and they kept us from getting after the puck quickly because of the interference they were running at the blueline."

"We cut them right off in the third period," said Islander Coach Al Arbour. "But they gave us a tough game. We got three quick goals, then they put the kid in goal, he made some big saves and it seemed to really lift their club."

"When Davy made those saves, we had life," said Washington winger Jean Pronovost. "The momentum started to go our way and, as a whole, we played much better. But we have to pass better in our own end and we have to get out quicker. When you're trapped in your own end, you invite mistakes."

"I just figured I'd do my best and try not to let them score," Parro said. "A lot of times a new goaltender can make some saves and get the guys going. I made two good saves early and we got some spark. I like a couple of hard shots like that right off the bat. It gets me right into things."

Green said the replay made up his mind to yank Palmateer, because he felt the goalie did not react on Tonelli's breakaway goal.

"We shouldn't have given the breakaway, but I didn't think he moved on it," Green said. "When you're down fast, you have to do something to get things going. The best way to give the guys a fresh start is to change the goaltender."

Green apparently read a large sign posted at one end of Capital Centre that read, "Let's Juggle Management Instead of Lines."

"I don't like changing lines," he said without a prod, "but if guys are not working or not performing with other guys, you can't continue to go with a losing horse."

After the game, the Capitals decided they had gone far enough with Jim McTaggart, an aggressive defenseman last season who has been a disappointment this fall. McTaggart, who was not part of the Capitals' five-defenseman alignment last night, was shipped to Hershey.