I am writing to voice my objection to "Doonesbury" on Sunday, Oct. 11. In the cartoon, G. B. Trudeau exhibited a gross and disgusting mass of people in an obvious display of sexual decadence.

Have we come to the point in our society when even the cartoon sections of major newspapers indulge in perversion and pornography? What right does The Post have to editorialize against child pornography, when the newspaper prints a cartoon that is obscene?

If The Post cares for children -- and there are thousands who read the Sunday comics -- then it will stop printing comics such as "Doonesbury."

Bruce H. Waldschmidt . . . Sexist . . .

So the little lady is still out in the kitchen, cooking her heart out and trying to please the family? A quick look at the comics of Sunday, Oct. 18, tells us that at least four cartoon writers continue to lock women into roles that other family members can and should be sharing. Not funny, boys!

Blondie turns to her family, asking what each wants for dinner; then she prepares the meal, leaving family members to read and watch television while she is in the kitchen. The mother in "Gasoline Alley" asks her children, "Have you decided what you want?" before tackling breakfast, while they sit and watch. Sally Forth is teased by her daughter because mom's pancake-making skills have deteriorated. Father sits offstage, and daughter waits to be served. And in "Momma," although necessary for the typical mother-in-law joke, it's again the wife serving up refreshments while husband sits and waits.

I am glad life does not necessarily reflect the "art" of the comics. Among families I know, there is some sharing of kitchen and serving chores, and "mother" is not alone at her home on the range. But I am sorry that our often unfunny "funnies" perpetuate such stereotypes.

It's just not funny!

Arleta S. DiPaolo . . . Elitist . . .

To discontinue "Luann" was a mistake for which my teen-age daughter will not soon forgive you. Your choice of its replacement constitutes a social misdemeanor.

"Zippy" is a tasteless attempt at philosophical elitism, illustrated in a style crudely reminiscent of that volunteered art form so ubiquitously displayed on the walls of public restrooms during the '60s.

Bowing to inevitable change, I now satisfy my own search for silliness among the excesses and maunderings of Robert Novak and James Kilpatrick, among occasionally and unintentionally hilarious broadsides by Patrick Buchanan.

But now, sirs, you have gone too far, striking a blow too foul to ignore. You have managed to misplace the Quote-Acrostic for Oct. 10, rerunning instead the previous week's offering.

Admittedly that was an unusually tantalizing puzzle, requiring rather more effort than usual; it was not, however, worth reprinting so quickly.

Sirs, you have ruined an avid Acrostic fan's Saturday morning. Shame on you.

John Studebaker . . . And Just Plain Offbeat

John Vetter manages to hit the nail on the pinhead yet still miss the point about ''Zippy'' {Free for All, Oct. 17}. What he describes as ''incomprehensible'' very nearly perfectly reflects, for me, the unpredictability of people and life's little surprises.

Who knows what's coming next? And would it make any more sense if you did? Therein, I think, lies the Zipman's appealing quality. Learn to enjoy the offbeat, the ''from out of left field'' aspect of it all.

Just lighten up, Vetter.

Bob McFadden