If Henry II's provocative lament about Thomas a Becket -- "Who will rid me of this troublesome priest?" -- were in the plural, it might describe President Reagan's attitude toward the Roman Catholic bishops meeting in conference here this week.

The president is deeply vexed by the bishops, who are insisting on writing to the 50 million members of their flock a pastoral letter on -- Heaven help us -- the morality of destroying God's earth by nuclear weapons.

Various members of the administration have excoriated the clergy for meddling in matters of strategy and have been telling them for almost a year that the future of mankind is none of their business. The bishops have, nonetheless, gone forward with composition of a letter warning of the consequences of the arms race and plan to take a final vote on it next May.

"Why," you can almost hear them saying at the White House, "don't they stick to things they understand, abortion and aid to parochial schools?"

"Where," they must ask when they gather in the Situation Room, "is Cardinal Spellman now that we need him?"

The late Cardinal Francis Spellman of New York, an unflinching supporter of the Vietnam war, was a pre-Vatican II cleric, one of those who in matters of war and peace, sided with the state. He epitomized an era when the U.S. hierarchy, faced with certain conflicting considerations in matters of state, asked itself whether a thing was good for the church or bad for the church. The new breed asks, instead, whether something is good for humanity or bad for humanity.

The bishops are headed straight for declaring that nuclear war is immoral. To Reagan, they have blundered into heresy. They favor a nuclear freeze.

The president had already paid his disrespects to advocates of the freeze. He may or may not have had the bishops in mind at his last news conference when he again voiced his opinion that such people, whether they know it or not, are doing the work of the Kremlin.

That has not deterred the bishops in their deliberations at the Capital Hilton Hotel. In fact, the White House offensive has had a contrary effect. Catholic priests are by definition, and through quite severe training on the matter, team players. Now a majority of the bishops, unaccustomed though they may be to challenging temporal power, has rallied behind its embattled brothers on the committee drafting the pastoral.

In retaliation, the White House launched its version of a first strike on the Roman-collared subversives, who walk to their meetings with breviaries under their arms. It took the form of a letter from national security adviser William P. Clark, which was delivered with some scanting of protocol -- they read it first in The New York Times yesterday.

The tone of the letter was odd, if not hilarious, when considered in light of the career concerns of those to whom it was addressed. Not everyone would undertake to lecture bishops on morality -- that, after all, is their turf, and their having gone cosmic hardly makes it less so. The bishops, having been informed that they know nothing of strategy, may not be entirely grateful for being told that they don't grasp the moral aspects of Reagan's nuclear policy, either.

Men who have grown hoarse preaching against the godless Soviet system may no more appreciate a chiding, for insufficient anti-communism, from the ex-seminarian in the White House.

But these lapses merely reflect the dismay of aides who know that the president's greatest disappointment in the recent election was the success of the nuclear freeze issue.

What may dismay the president and his men even more is the bishops' polite but unflinching advance in what they obviously consider their "just war" with the White House.

Archbishop Joseph L. Bernardin of Chicago, head of the drafting committee, served notice in various mild but unmistakable ways that they are not going to be pushed around. "We are not intimidated," he observed cheerfully.

How did he and his brothers feel about being designated, because the president did not distinguish among freeze advocates, as unwitting agents of the Kremlin? Bernardin absolved Reagan of smearing the bishops and ended on an airy note that indicated that red-baiting won't work anyway.

"I don't worry about things like that," he said equably and charitably explained the president's excesses.

"It is inevitable when you discuss matters of this kind . . . there is going to be a great deal of feeling," Bernardin said.

"It makes the process a little more interesting," he added philosophically.

And how did the bishops feel about charges that they had misread the administration's disarmament negotiations in Geneva?

"We will see who is misreading whom in due course," the archbishop replied dryly.