Assistant Attorney General William Bradford Reynolds defended the administration's civil rights policy yesterday before the Anti-Defamation League of B'nai B'rith, charging that racial quotas are unconstitutional and promote racial disharmony.

"That this administration opposes preferential treatment based solely on race . . . is well established. We apologize to no one . . . . The Constitution guarantees equal treatment under the law, and any compromise of that ideal delays the day when we can truly promise our children a society of racial harmony and equal opportunity," Reynolds said.

"The more insistent government is on the use of racial preferences . . . , the more racially polarized a society becomes. Such a selection process encourages us to stereotype our fellow human beings, to view their advancements not as hard-won achievements, but as conferred benefits . . . . It submerges the vitality of personality under the deadening prejudgments of race," he said.

Reynolds' speech was received enthusiastically by the Anti-Defamation League, which has long opposed quotas despite a history of strong support for civil rights. In the past, quotas have been used as a way of discriminating against Jews.

Kenneth Bialkin, national chairman of the ADL, said in an interview that his organization does not side with the Reagan administration on every civil rights issue.

For example, the ADL does not share the administration's opposition to school busing as a desegregation tool and opposed the administration on the Bob Jones University case over giving tax exemptions to schools in which racial discrimination occurs.

But on the issue of reverse discrimination and racial quotas, Bialkin said, the administration is "on the right track . . . . We've been there for a long time . . . . We've felt very strongly that the seeds of societal destruction and discord lie in a man-made quota system . . . . Who's to watch the watchmen?"

Civil rights groups repeatedly have criticized the Reagan administration for rejecting the use of numerical goals and quotas in remedying past employment discrimination. Instead, Reynolds has pushed for minority recruitment programs. He also has expressed a willingness to bring lawsuits on behalf of individual victims of past discrimination.

Bialkin said the ADL position on racial quotas has made the group something of an outcast among other civil rights groups with which it normally works closely. ADL is a member of the 165-organization Leadership Conference on Civil Rights.

"We are not happy at having to disagree with a lot of our colleagues in the Leadership Conference. We intend to be up front and fight as hard as any of them for vindication of civil rights in this country," he said.

"There is a significant group in the civil rights movement leadership who feel fiercely that a national policy of quotas and preferential treatment for blacks, particularly, is essential for the redress of past evils and that any move to weaken that movement is deeply resented. The intensity of this attack on the ADL is a reflection of that strongly held view . . . .

"I'm not saying the people are evil who oppose us on this issue," Bialkin said. "But we don't intend to be intimidated on the quota issue . We will not be pushed around . . . .We hold the view that . . . discrimination and prejudice have to be eliminated from our society . . . but racial preferences and quotas are the wrong way to do it--it is wrong constitutionally, it is wrong socially and it is wrong ethically."