The news that the FBI was doing wholesale spying on Americans who disagreed with President Reagan's Central American policies is both disgusting and ominous: disgusting because the FBI told us it wasn't going to do that anymore, and ominous because William H. Webster, who was FBI director at the time, is now in charge at the CIA.

After the revelations uncovered by the Church Committee of the most egregious Vietnam-era abuses of surveillance, wire-tapping and black bag jobs, Congress was looking for a white hat. They thought they had found one in Webster, a Republican and a federal judge, who was presumably aware of constitutional rights. Webster, who has straight-arrow good looks and a soothing manner, lavished on them the assurances they craved.

"The lesson has been learned," he declared. The bureau would no more step out of line to harass citizens out of step with unpopular wars.

Now, however, more than 1,000 documents obtained by a New York group called the Center for Constitutional Rights tell us that the Federal Bureau of Investigation has been going with its old nasty reflexes. A particular target, among hundreds under suspicion, was called CISPES, or Citizens in Solidarity with the People of El Salvador. The FBI was so concerned about the danger posed by CISPES that it infiltrated an agent named Frank Varelli into the Dallas office. He was paid $1,000 a month to get the goods on the dissidents.

Congress, and everyone else, has long known that the FBI was leaning on Americans who defiantly continue to visit Nicaragua and try to repair the damage of Reagan's war. They met delays at customs, with notebooks and address books briefly confiscated, presumably to be copied. Many returned travelers received unannounced visits at their offices by FBI agents. One found G-men telling her supervisor that it was "a matter of national security."

In 1987, when the chilling practice could no longer be ignored, House Judiciary civil rights subcommittee Chairman Don Edwards (D-Calif.) held hearings. He told the FBI to "knock it off." But there was no particular fuss or stinging report, and now Edwards is calling a new inquiry.

"I don't think the FBI came clean with us," Edwards said.

"I guess Congress was too good to Webster. We want to think well of him. But we're going to call him on this." As of this writing, Webster has not deigned to respond to the documented allegations.

Dissidents are looking back on mysterious break-ins of churches supporting the Sanctuary movement, by intruders who took only files and membership lists and left cash lying around. In November 1986, the Washington office of the Commission on U.S.-Central American Relations, headed by former ambassador to El Salvador Robert E. White, was raided by persons still to be found.

White was present when the bodies of four U.S. churchwomen, murdered by Salvadoran security forces, were dug up in December 1980. Two of the women belonged to the Maryknoll Order, which along with the United Auto Workers, the Catholic Archdiocese of Cleveland, the National Education Association and many other respectable groups was watched.

The documents suggest that it was zeal at the top rather than in the field that kept the "investigations" going when no criminal activity could be found. Keep looking, headquarters ordered.

It is disquieting to know that the head of the CIA is a man who sees in the Maryknollers a threat to the Republic.

Webster had no reason to think he would upset the White House by unleashing the G-men against the president's critics.

Never one to rock the boat, he ignored a hint from his FBI deputy that Lt. Col. Oliver L. North might be the subject of criminal investigation one day. After the bungled investigation of White House Iran-contra intrigues, he assured us that his men had found no evidence of document shredding.

The president, through his spokesman, has said he is dismayed at the news of five years of shabby sleuthing. Who would have thought it, especially Webster.

An "upset" Reagan has provided the ultimate howler: He asked Attorney General Edwin Meese III to look into FBI offenses. Meese is trying to scramble out of a new pit, allegations he knew about a Middle Eastern pipeline bribe suggested by an old friend.

Meese's confirmation hearing showed a man who couldn't manage money. What that taught him, apparently, was to seek any way of finding more.

No lessons learned there, either.