As St. Louis strives to become the Silicon Valley of the Plains, there's one thing to avoid: the pervasive sexism of the West Coast entrepreneurial capital. Critics, and naturally the most vocal are women, point to such flagrant examples as breast-peeping apps and lap dancers trotted out at tech conventions.

This should not be dismissed as mere-boys-will-be-boys behavior. It's more than that. It's a culture that has been created to stroke men's libidos and to pander to their baser instincts. As though there isn't already enough of that in the culture at large. Save it for the bars.

Sexism in Silicon Valley discourages women from getting involved in the burgeoning industry, which will have long-lasting effects on the types of technology that will move forward, as well as on the business models that are being developed.

The high-tech center is known as a frat-boy fantasylandwhere smart nerds rule. In the self-belief that the industry embodies meritocracy, the men who run it have sidelined women and some racial minorities. The result is some jacked-up version of the 1950s, where women are treated like window-dressing or worse, and a few figurehead women have been allowed to head tech firms — Marissa Mayer at Yahoo, Sheryl Sandberg at Facebook and Meg Whitman at Hewlett-Packard.

Below them, the numbers dwindle. And it's not just in the corporate offices or worker hives. The compositions of boards of directors offer another example of the men's-club mentality — about half of the publicly traded technology companies, including Twitter, have all-male boards.

The sexism charge is in the spotlight thanks to Ellen Pao, a venture capitalist and junior partner with the uber successful Kleiner Perkins Caufield & Byers. Late last month Ms. Pao lost a three-year-long legal battle with the firm; she had been seeking $16 million in damages in a sexual discrimination lawsuit.

Local angle — Ms. Pao's former mentor and head of the firm, partner John Doerr, 63, is a St. Louis native and graduate of Chaminade College Preparatory School. With a fortune valued at $3.4 billion, Forbes ranks Mr. Doerr as the 167th richest person in America.

Ms. Pao's case riveted Silicon Valley and, despite her loss, prompted some soul-searching among the brainy boys. While her trial was underway, two other discrimination cases, one each against Facebook and Twitter, were launched.

The numbers support the critics. From 1990 to 2011, women's share of jobs in software and computing fell from 34 percent to 27 percent. A study by Babson College showed the proportion of women partners in venture capital firms declined from 10 percent in 1999 to 6 percent in 2014. In the 92 most successful such firms, only 4.2 percent of the partners are women, says a survey by Fortune magazine.

Correspondingly, studies show that women are seeking fewer degrees in computer and information sciences. In 1985, 37 percent of undergraduate degrees in those fields were awarded to women; in 2010 that figure was 18 percent.

This is not the sexism of "Mad Men." It's more subtle and has been labeled "soft" sexism. Social scientists say it takes basically two forms. One describes women by traditionally stereotypical characteristics, such as warm, caring, deferential, emotional and sensitive.

Nothing wrong with those traits except when they are applied to women who are performing jobs usually held by men. When women don't exhibit those traits in the workplace, there is dissonance and men don't see them as having the qualities needed to perform the job.

The second form of soft sexism is prescriptive, when women take on traditionally male jobs and are labeled with terms like "brusque" or "uncaring." The result is they are not liked and get little support.

In Ms. Pao's case, she did everything the books tell women to do and was still penalized. She had impeccable academic credentials, including a bachelor's degree in electrical engineering from Princeton University, a law degree and an MBA, both from Harvard.

When a co-worker made unwanted sexual advances, she reported it to her supervisor. She asked for sexual-harassment educators and outsiders to investigate her claims. Afterward, she said, the company retaliated.

She claimed she was told that women were not invited to a firm event because they "kill the buzz"; she was left out of the loop on a business issue by the co-worker about whom she had complained; and she was poorly evaluated in a performance review.

An independent human resources consultant told her to drop her complaints because the company would do nothing and she would hurt her chances for success with the firm. When that happened, she filed a lawsuit and then was fired.

It may be difficult for a jury to empathize with a woman whose compensation package in 2012 was $560,000, just as it was for a St. Louis jury that found against Francine Katz, a lawyer and Anheuser-Busch vice president who sued the company in 2009 saying she had been underpaid because of her gender.

Ms. Katz's compensation package in 2002 was more than $1 million, still 46 percent less than the company paid the man who preceded her in the same job.

There needs to be a new feminism to combat the new soft sexism. Women must step up and start demanding equal rights for themselves, their sisters and their families. Women in Missouri make 71 cents for every dollar a man is paid. Of the estimated 950,000 Missourians who live in poverty, 55 percent are women.

The problem may get more attention when it is in the board rooms and technology valleys, but it means more for women who work in the retail mines and fast-food lines. More women at the top would help more women at the bottom. That form of trickle-down benefit is real.

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