THE NAVY'S BEHAVIOR in the case of Lawrence Korb was truly tawdry. Navy officials hounded this former assistant secretary of defense out of a job with a captive and spineless defense contractor because he had dared -- rather mildly, and for the most constructive of reasons -- to disagree with them. They look back on this achievement now with pride, as a show of strength. It is a sign of serious weakness instead.

Mr. Korb had been assistant secretary for manpower from 1981 to 1985. He resigned to join the office here of Raytheon Co., this year's third-largest defense contractor. With Raytheon's permission he also joined the board of the Committee for National Security, a small and mostly liberal public policy group. In February he then lent his name to a CNS report on the defense budget. The report took as a given that the president's defense request to Congress would be cut. The question it asked was how to cut most sensibly. It said (as have many others) that it would be better to put off buying some of the new generations of weapons the Pentagon wants than to hollow out the services by cutting operating funds. It argued that it would be possible to make such weapons cuts without disastrous loss of capability. It urged as a moderate course that the defense budget be allowed to rise with inflation.

Mr. Korb, whose presence gave the otherwise routine report an extra edge, emphasized that his purpose was not to undo the defense gains of the first Reagan term, but to protect them. That did not propitiate Navy officials; one of the likely casualties of tighter budgets is their cherished goal of a 600-ship Navy. Assistant Navy Secretary Everett Pyatt sent a letter to a Raytheon executive, saying "The Navy objects strongly to officers of our contractors whose salaries are paid in part by Department of Defense, speaking as company officers, attacking President Reagan's program." Mr. Pyatt also "called Raytheon and I said I wondered when you started kicking the customer around. We had a competition going on for a couple of missiles, and Raytheon was a player." Assistant Navy Secretary Melvyn Paisley called to complain as well. Raytheon's defense sales are now more than $2 billion a year, and more than a third of its business. The company quickly gave in. The CNS report was issued Feb. 25. Twenty-three days later the company announced that Mr. Korb had been moved from vice president to special adviser; he has now left to become a dean at the University of Pittsburgh. Navy Secretary John Lehman later called Mr. Korb to say weakly that he thought Raytheon had overreacted. Mr. Pyatt made no such effort to soften the record. "I didn't much care," he said the other day when asked whether he thought his complaints would cost Mr. Korb his job. "I felt good afterward."

The message in all this is pretty clear. The dividing line between Defense Department and defense contractors is paper thin. The department will use its power as chief customer to control expression. You dissent at your peril. It is an abusive system that discredits the defense policy in whose behalf it was invoked.