With 23 years in the Marine Corps, the Semper Fidelis juices of Sen. John Glenn (D-Ohio) are astir. A veteran of two wars, the senator believes he and his colleagues are under unfair attack by Caspar Weinberger. The secretary of defense has a spokesman, Michael Burch, who said, "Secretary Weinberger feels that those who hope for 'success in bringing down the defense budget' really mean success in weakening the security of the country."

Those words sent Glenn to the Senate floor to say that the military-budget debate had taken "an ugly turn." Citing his own war record, as well as others, Glenn said, "We all deserve better than to have our motives and our loyalty challenged by officials in the Reagan Defense Department simply because we may not agree with their assessment of how much money the Pentagon needs in 1986."

Glenn demanded a retraction and apology from Weinberger. When none came, he confronted Weinberger a few days later in Senate hearings and repeated the demand.

Weinberger again said no. He is right. The military debate has taken not an ugly turn, but an inevitable turn. It has been senators like Glenn who, one military vote after another and approving one weapon deadlier and bigger than the last, have sanctioned the spending of approximately $1 trillion for the military in the past four years.

Such obedience to the Pentagon and its military contractors creates a stage onto which a one-note performer like Weinberger would inevitably sing and dance. When the applause suddenly tapers slightly, naturally he is stunned. Naturally, too, he adds insult to infamy by striking out at the senators whose smiles at his performace are now a millimeter thinner.

Why shouldn't Weinberger challenge their loyalty, when they have been loyal buyers of the Reagan line: that weapons production shouldn't be slowed because of "the message" it sends to the Soviets; that "the Russians are ahead"; and that his simplistic view of history is correct -- "No nation which put its faith in treaties but let its military hardware deteriorate stayed around very long."

America's war-preparation economy didn't need Caspar Weinberger to flower. He offends a few warrior-politicians like John Glenn because of inflexibility. Weinberger replies that he has already cut a flexible $36 billion out of the current budget. Despite the appearance that it's Weinberger vs. some anti-Pentagon doves in Congress, the reality is that compatibility, not combat, is at work. Sen. William Proxmire (D-Wis.), after endorsing Glenn's call for an apology and a retraction, said that he knows of no one in the Senate "who does not agree that we need an increase" in military spending. "The talk is only about how much."

There is the compatibility. Studies by such independent groups as the Brookings Institution report that $40 billion can be cut from the military budget without impairing the armed forces effectiveness. In 1982, ad hoc hearings held by Rep. Ronald Dellums (D-Calif.) advised a figure of $50 billion for the first year. Those numbers represent minor tamperings, cuts that are nothing compared with the slashes and gashes in the proposed reductions in domestic spending in the new budget. In this season of homelessness and increased mortgage foreclosures, a 46 percent cut in funds for the Department of Housing and Urban Development has been called for by the Reagan administration.

Despite that, no one in the Senate has the political courage to call for a decrease in military spending. With a $2.5 trillion national debt expected by 1990 and a 1986 Pentagon budget rising by $30 billion to $277 billion next year and $418 billion in 1990, the bravest talk to be heard is a fret or two about "slowing the increase." This is true even among the senators who have 100 percent voting records from peace groups.

With a military booster like Glenn posturing as the voice of sanity against Pentagon excess, dissenters of genuine reason are pushed further to the fringes. But they continue to speak. David Cortright, the director of SANE, says of the current madness: "Once again, President Reagan is blatantly distorting the facts to suit his political purposes. He claimed in a radio broadcast of February 2 that the Soviets are engaged in 'the greatest military buildup in the history of man.' Yet his own CIA reported in September 1983 that Soviet military spending has increased by only 2 percent a year. In the last four years, the U.S. arms budget has increased by an average of 9 percent a year above inflation."

Glenn's calling for an apology and retraction from Weinberger would be meaningful if some dissent truly were present. Dissent suggests independent thinking, but with no one getting close to calls for decreases, go-along loyalty to the Pentagon remains the prime Senate instinct. It's near to being a mating call.