BECAUSE IT IS DEFENDING the First Amendment rights of a band of local Nazis in Chicago, the American Civil Liberties Union is facing a crisis. Both the Illinois office and the national office have been deluged with fiercely critical mail, including letters of resignation from at least 2,000 ACLU members across the country. ACLU officials expect that as many as twice that number will resign. And the work of the Illinois chapter, if members there continue to resign in large numbers, will have to be curtailed. The ACLU has prompted this extraordinarily remaining faithful to a principal tenet; that American citizens have a constitutionally protected right to freedom of speech, expression and peaceful assembly.

Specifically, the Illinois ACLU chapter is defending the right of the American Nazi Party in Chicago to stage a march in the Chicago suburb of Skokie without having to meet such unusual conditions as, for instance, posting a $350,000 bond that Skokie public officials imposed on the Nazis. Most of these restrictive conditions have been unpheld by the Illinois Appellate Court. The ACLU is appealing to the Illinois Supreme Court, which will hear the case next week.

What has made this controversy so painful and intense is that Skokie's population is heavily Jewish and that a significant number of its Jewish residents are survivors of Hitler's death camps. Their loathing for the Nazis' inhumane beliefs and their outrage at the Nazis' plans to parade in their community are sentiments easy to understand and also to share - which we do. But they do not justify efforts to deprive the Nazis of their constitutional rights. As ACLU Executive Director Aryeh Neier (himself a refugee from Nazi Germany) has said, civil liberties represent the antithesis of Nazizm. Freedom of speech cannot be limited to just those whose views the majority finds acceptable. If the Nazis, as they have said, intend to march peacefully, then they have a right to march without undue restriction.

The actions of Skokie's public officials in this matter are, to some extent, understandable. But the response of the ACLU's critics, especially its erstwhile members, is truly disturbing. Presumably, they had some sense of the ACLU mission, of the importance of defending the right of free speech for those you don't agree with. Are there now to be groups and individuals who can be deprived of their constitutional rights? And, if so, who is to make such decisions? Mr. Neier and his two colleagues in Chicago, David Hamlin and David Goldberger, are right in their perception of what is really at issue in Skokie: not the rights of a despicable bunch of Nazis, but the rights of Americans generally to freedom of speech, expression and assembly.