They hummed along while Kate Smith sang "God Bless America," hissed at Ted Kennedy's face, groaned when Jimmy Carter kissed Leonid Brezhnev on the cheek. And when Ronald Reagan told them, "We have every right to dream heroic dreams . . . We are Americans," they cheered and cheered.

It was the premiere of the National Conservative Political Action Committee's new movie, but no one was worried about the audience response. About 200 loyal NCPAC supporters gathered at the Watergate Hotel last night for a $250-a-seat dinner to salute House and Senate members who have supported President Reagan's programs. Any movie whose theme song had lines like "Ronald Wilson Reagan/ U-S-A and number one" was certain to be a hit with this crowd.

"Our plans are different from '80," NCPAC chairman Terry Dolan said before the dinner. "Our basic focus will be on the positive side of Ronald Reagan. In '80 we found that people didn't know enough, didn't know anything, about their representatives. They didn't know if they were conservative or liberal. They didn't know what they stood for. Now, people know too much about Reagan, and most of it is wrong."

As Dolan sees it, the country is filled with unsung heroes, so he titled NCPAC's '84 campaign "American Heroes for Reagan" and made a movie to kick off the campaign. The 30-minute film, called "Ronald Reagan's America," has already been shown in Houston and will be aired here in late July on Channel 5.

When Dolan introduced Rich DeVos, president of Amway Corp., to the audience, he called DeVos "living proof of the existence of American heroes." In his remarks, DeVos decried the way the media have "managed to make heroes of those who are not achievers in our society.

"I don't believe success is sinful," he said. "The problem in government today is that we punish achievement and praise those who fail. If I am poor, I can't help anyone."

Earlier, Dolan told the audience, "Our campaign is designed to do the things the American media is not doing, and that is to give Ronald Reagan a fair break." He singled out The Washington Post as particularly guilty of what he called "shoddy, reckless and inaccurate reporting." Dolan accused The Post of misrepresenting NCPAC's achievements in the '82 elections, and said the paper refused to answer his charges.

As the audience applauded and cheered, he encouraged reporters in the room to ask The Post "why they will not follow the same standards of fairness they demand of everyone else."

Describing what he called "a media conspiracy against Reagan," Dolan said, "For the last few weeks they have published on the front page a rather silly story about a campaign book which no one particularly cares about, including the speaker of the House."

The audience cheered again.