General Motors Corp. Chairman Thomas Murphy, in a Washington address yesterday that amounted to a state of the nation assessment from one of the country's leading industrialists, said he is convinced the 1980s "will finally force a whole series of constructive decisions" on the American people.

Issues of concern to business, government and other areas of national life will be confronted early in what he forecast would be a "decade of decisions" -- in contrast with the "me decade" of the 1970s when Murphy said the only action taken was "a little putty here and a quick patch there to get us through the worst of an immediate crisis."

The GM chief executive also said he finds "almost no parallels at all" between the nation's economy today and in 1975, the depth of a deep recession. Despite the "myopia" of economists and a "hunger for bad economic news [that] mystifies me," the economy expanded last year, unemployment is little changed, exports expanded and the trading deficit was lower, he declared.

A "sharp and dramatic" difference between today and five years ago is that business has kept inventories in fairly close balance with sales and the U.S. now is experiencing "a period of slow economic growth, after nearly five years of continuous expansion," according to Murphy. If a slowdown occurs in coming months it should be short-lived and will be followed by "a resumption of rather strong growth -- before the end of the year."

Economic decision-makers in Washington might want to study such economic plus factors and "not just the negative," he advised further.

Speaking at Georgetown University, where he was honored as "business leader of the year" by the School of Business Administration, Murphy also condemned bitterly the activities of highly organized special-interest "zealots" that reduce the most complex public issues -- inflation, energy, arms limitation, the environment -- to several words on a placard and street demonstrations "arranged for the cameras, timed to coincide with television news deadlines."

Although he did not refer specifically to a "big business day" being planned by some activitist groups across the nation on April 17, Murphy described it as just one example of "shortsightedness" by the special interests.

"They are going to break so-called 'big business' up into a series of small cottage industries, and with these 18th-Century sized companies they are going to expect that we attack 20th-Century sized problems," he observed.

"Many of these zealots have been born and raised in affluence -- affluence achieved not by their efforts but by inheritance," Murphy went on. "They are quite satisfied with their state of life -- and would consign the less fortunate forever to a lower, even a decreasing, standard of living," said Murphy, since the thrust of militant special-interest groups is "against anything and everything that could contribute to greater economic growth."

But the holding of Americans hostage in Iran and "sudden aggressiveness" by the Soviet Union have done much to refocus thinking and the decade ahead should be more rewarding, Murphy stated.

Among the most pressing issues that should be confronted in the next few years according to Murphy, are the following:

The combination of rising oil prices and use of oil as an international political instrument will expand pressure in all nations to export goods and the U.S. must decide how much encouragement will be provided to business for increased productivity and strengthening the world competitive position of American employers.

Since chief world competitors have been outpacing the U.S. in capital spending for more modern facilities, this country must act to encourage similar investments -- with tax incentives, an end to double taxation of dividends and reduction of capital gains taxes.