In his Aug. 25 column, Nat Hentoff describes the legal struggle of a pro-life college professor who refused to pay dues to his union, which has passed a resolution favoring pro-choice on the abortion issue. Mr. Hentoff didn't give much of an indication of his own evaluation of the issues, except for a barely perceptible hint in his last sentence, when he sums up the struggle as pitting the union against a professor who was waging an "uphill battle to get back a job he could have kept only at the cost of his self-respect."

Quite to the contrary. If the principle of "self-respect" applied to all of us and our convictions, then convinced pacifists (who also hold life sacred) would be justified in withholding their taxes to a federal government that invades Caribbean and Central American countries.

There are a number of parallels between the two situations. The government is obliged, practically speaking, to provide the same services to all its citizens, whether or not they pay their taxes. Under federal labor law, the union is under the same obligation to provide equal services to all members of the bargaining unit it represents, even if individual members refuse to pay dues.

The federal government is governed by freely elected officials, who pass laws and fund operations. Labor unions are compelled by law to elect their officers freely and pass resolutions by majority vote of their governing bodies.

Besides civil disobedience (not paying taxes or dues), there is another option for the pacifist and the professor. Both should achieve their goals within our democratic system -- and bolster their self-respect -- by working to mobilize support for alternative governing officials and alternative legislation. Democracy offers opportunity, not a sure thing, and if the pacifist and the professor at first lose, they should try and try again -- meanwhile paying their taxes and their dues. HOWARD D. SAMUEL President Industrial Union Department, AFL-CIO Washington