Sen. Howard M. Metzenbaum (D-Ohio), all white-maned indignation, paused in his tirade to say the ultimate thing to William Bradford Reynolds, assistant attorney general in charge of the Civil Rights Division: "I don't know if you dislike blacks."

Reynolds, at Judiciary Committee hearings on his nomination to the Justice Department's No. 3 job, associate attorney general, did not address Metzenbaum's wonder, which is shared by students of Reynolds' record as the guardian of the country's civil rights.

Metzenbaum's bony face reddened as he pressed for an explanation of what he called Reynolds' "obscene" and "shameful" decision to allow a Selma, Ala., polling place to be switched from a black neighborhood to a white one.

Reynolds, a smooth, chilly man who faithfully represents President Reagan's smooth, chilly attitude toward civil rights, contented himself with observing that Selma has changed in the 20 years since Metzenbaum marched with Martin Luther King Jr. to secure voting rights for blacks.

"You don't seem like a bigot," Metzenbaum said. "You seem like a decent man."

Selma may be the most flagrant case in Reynolds' bulging portfolio of attempts to turn back the civil rights clock.

He gave early notice of his bent with his bizarre notion of preserving a tax exemption for segregated Bob Jones University in Greenville, S.C. In the opinion of civil rights activists, he has done as much for oppressed minorities as Cathleen Crowell Webb did for rape victims.

On job quotas, busing and affirmative action, there is some dispute. On voting rights, all resistance had died down. The Selma case, Metzenbaum argued, defies explanation except on racial grounds.

The polling place, located in a community center in a black neighborhood, seemed ideal. But after a strong showing by blacks in a local election, an all-white commission decided to transfer it to the Dallas County Courthouse, opposite the sheriff's office. Reynolds' approval was needed, and he gave it.

The episode had an air of Bitburg about it: An effort to repair something that was not broken, opening old wounds in the process.

Reynolds' legal staff objected to the change, with reason.

The results were dramatically negative. Voting in that precinct fell from 55 percent in 1980 to 36 percent last year.

"The falloff didn't mean a damn thing to you?" Metzenbaum asked.

Reynolds in a memo had dimissed any linkage as "a fanciful conclusion," but to Metzenbaum he said noncommittally that he didn't know "why voters do or do not vote . . . . A falloff could be triggered by any set of circumstances."

He indicated that too much was being made of the move to the "neutral" courthouse, which he said was three-quarters of a mile from the old polling place and had more parking. Yes, black voters had been harassed at the courthouse, but it had been recorded by Justice Department observers, which Reynolds seemed to think proved he was on the job. The presence of observers, he suggested, was more striking than the scandal of voter intimidation, which the Voting Rights Act was drawn up to prevent.

Sen. Edward M. Kennedy (D-Mass.) brought to Reynolds' attention to the fact that it was a $5 cab ride for black voters to get to the courthouse.

Metzenbaum referred to the intimidating proximity of the sheriff's office to the new polling place. Selma, he reminded his cool witness, was where blacks had encountered some of "the most brutal treatment" of the civil rights struggle.

Reynolds was beyond the reach of reminiscence. He is, after all, an official in the Reagan administration, where insensitivity toward one's constituency is considered commendable, as Reynolds' promotion would attest.

He sketched himself as a man with a conscience exquisitely tuned to the finest nuances of the law. In the Bob Jones case, he was troubled by the possibility that the Internal Revenue Service had gone beyond the intent of Congress and did not have the authority to deny the tax breaks. The Supreme Court contradicted him, 8 to 1.

Selma, he suggested, did not rate any sophistry. He had merely assented to a "local decision." That wins you points with Ronald Reagan, who also thinks he is much misunderstood on the matter of civil rights.