Could this movie possibly fall into the category of a conspiracy; that any fictional parody of male behavior (which this surely is, at least in part) becomes in fact a parody of female behavior as well? Is that what irks feminists about the Stepford Wives?

And no matter what the answer to that question is, the "horror" aspects of this 1975 film were balanced, and even matched, by the ideological aspects. Whether one views the film as a statement on that cadre of men who are control freaks, or that element of the female gender hopelessly submissive to the whims and demands of men, the film has a strong ideological theme.

And moreover since ideology is part of the political world, and the political issues of the day seem to always creep into film, the Stepford Wives, as a feminist-themed film, is ideological. Feminists always have a fierce political agenda, and part of the horror of this show is that it uses "mind control" to keep women down. In his book, the Monster Show: A Cultural History of Horror, author David J. Skal discusses the various "scares" in American society...

The "bomb scare" produced monsters that became gigantic and menacing because they were doused with radiation; the "red scare" created mind-controlling strange monsters from space, Skal points out, who were actually meant to parody communists, whom everyone believed had the patent for mind-control.
But the "scare" in the Stepford Wives movie (women's liberation scares some men) could actually go both ways: feminists might be afraid that men will grab even more power through the compelling film image of lovely female robots doing what their successful husbands expect and demand that they do, what a lot of men would like to have their wives do; and, conversely, men could be afraid that feminists will get the upper hand as a result of repugnant responses from the average woman when she sees the movie's portrayal of female robots cow-towing mindlessly, subserviently to the whims of stogy, boring men.

References

Skal, David J. The Monster Show: A Cultural History of Horror. New York: W.W.

Norton and Company, 1993.