The past two decades have been an experiment in corporate behavior modification. An array of well-intentioned organizations such as CERES promoted the idea that large companies could be made to do the right thing by getting them to sign voluntary codes of conduct and adopt other seemingly enlightened policies on environmental and social issues.

At first there was resistance, but big business soon realized the advantages of projecting an ethical image: So much so that corporate social responsibility (known widely as CSR) is now used as a selling point by many firms. Chevron, for example, has an ad campaign with the tagline “Will You Join Us” that is apparently meant to convey the idea that the oil giant is in the vanguard of efforts to save the earth.

What also made CSR appealing to corporations was the recognition that it could serve as a buffer against aggressive regulation. While CSR proponents in the non-profit sector were usually not pursuing a deregulatory agenda, the image of companies’ agreeing to act virtuously conveyed the message that strong government intervention was unnecessary. CSR thus dovetails with the efforts of corporations and their allies to undermine formal oversight of business activities. This is what General Electric was up to when it ran its Ecoimagination ads while lobbying to weaken air pollution rules governing the locomotives it makes.

Recent events put into question the meaning of a commitment to CSR. The company at the center of the Gulf oil disaster, BP, has long promoted itself as being socially responsible. A decade ago it adopted a sunburst logo, acknowledged that global warming was a problem and claimed to be going “beyond petroleum” by investing (modestly) in renewable energy sources.  What did all that social responsibility mean if the company could still, as the emerging evidence suggests, cut corners on safety in one of its riskiest activities—deepwater drilling? And how responsible is it for BP to join with rig owner Transocean and contractor Halliburton in pointing fingers at one another in an apparent attempt to diffuse liability?

BP is hardly unique in violating its self-professed “high standards.” This year has also seen the moral implosion of Toyota, another darling of the CSR world. It was only months after the Prius producer was chosen for Ethisphere’s list of “the world’s most ethical companies” that it came to light that Toyota had failed to notify regulators or the public about its defective gas pedals.

Goldman Sachs, widely despised these days for unscrupulous behavior during the financial meltdown, was a CSR pioneer in the investment banking world. In 2005 it was the first Wall Street firm to adopt a comprehensive environmental policy (after being pressured by groups such as Rainforest Action Network), and it established a think tank called the Center for Environmental Markets.

Even Massey Energy, which has remained defiant in the face of charges that a preoccupation with profit over safety led to the deaths of 29 coal miners in a recent explosion, publishes an annual CSR report.

When the members of a corporate rogues’ gallery such as this all profess to be practitioners of CSR, the concept loses much of its legitimacy. The best that can be said is that these companies may behave well in some respects while screwing up royally in others—the way that Wal-Mart is supposedly in the forefront of environmental reform while retaining its Neanderthal labor relations policies. Selective ethics, however, should be no more tolerable for corporations than it is for people.

Heaven forbid that we violate the free speech rights of CSR hypocrites, but there should be some mechanism—perhaps truth-in-image-advertising laws—to curb the ability of corporations to go on deceiving the public.

This is the implicit message of the cover of the new issue of Newsweek, which is filled with leaves to promote its feature on “The Greenest Big Companies in America: An Exclusive Ranking.” The list itself, however, has more validity than the usual exercises of this sort, which tend to take much of corporate greenwash at face value.

The Newsweek rankings are based on what appear to be solid data from KLD Research & Analytics, producer of the reputable (but expensive) SOCRATES social investing database, along with Trucost and CorporateRegister.com. Each company in the S&P 500 is rated on its environmental impact, its environmental policies, and its reputation among corporate social responsibility professionals, academics and other environmental experts. The ratings even take in account a company’s “regulatory infractions, lawsuits and community impacts.”

Not surprisingly, those at the top of the list are high-tech companies—such as Hewlett-Packard (ranked No. 1), Dell (2), Intel (4), IBM (5) and Cisco Systems (12)—which have never had quite the same pollution problems as old-line industries and which in many cases have made themselves “cleaner” by outsourcing their production activities to overseas producers.  Dell, in particular, is on its way to becoming a hollow company by selling off its plants.

More interesting is that supposed sustainability pioneer Wal-Mart comes in at No. 59, behind old-line industrial companies such as United Technologies and Owens Corning. Whole Foods Market, purveyor of over-priced organic groceries, is a bit lower at 67. Oil giant Chevron, which urges the public to “join us” in its supposed commitment to energy efficiency, is ranked 371, not much better than long-time global warming denier ExxonMobil (395).

Since the Newsweek list covers the entirety of the S&P 500, we can also look at what is probably the most significant group: those at the very bottom. The harm that these companies—especially utilities such as American Electric Power and Southern Company with lots of fossil-fuel-fired power plants—do to the environment far outweighs any good done by those at the top of the list. Also among the laggards are agribusiness giants Monsanto (No. 485), Archer Daniels Midland (486), Bunge (493) and ConAgra Foods (497).

But special mention must be given to the absolute worst company of all: mining giant Peabody Energy. On a scale of 0 to 100, Peabody is awarded all of 1 point, presumably reflecting its single-minded dedication to climate-destroying coal and its support for groups fighting the climate bill now in Congress.

Newsweek deserves credit for undertaking a serious evaluation of corporate environmental performance. The web version even has a nice sidebar on green fakery. But the magazine could have easily turned the list upside down and headlined its feature “The Biggest Environmental Culprits of Corporate America.”

It is indeed the case that the site allows reader comments that are critical of certain company practices. For example, a posting by an “associate” named Alex saying he might use spend his federal economic stimulus check to purchase a TV or a laptop was followed by comments on how that would do more to help the foreign economies where such products are made. One person asked: “what happened to the campaign WalMart used to run advertising its committment to support American manufacturers?”

Yet, it appears that the Times was hoodwinked by Wal-Mart. The appearance of authenticity and candor is just another technique used by advertising agencies and public relations consultants to win over skeptical audiences.

As for those critical comments, it’s significant that “Alex” thanked all those who had corrected a spelling error in his post but had nothing to say about the company’s sourcing practices. In fact, that the only real topic covered in the posts apart from product assessments is “sustainability.”

Those items are posted in the name of Rand Waddoups, who is no lowly buyer but rather the company’s senior director of business strategy and sustainability. His part of the blog, at least, fits in neatly with the company’s dubious campaign to depict itself as the environmental leader of the corporate world.

As I have previously noted, Wal-Mart’s green crusade places all the burdens on its suppliers, while the moves taken by the retailer itself (improving energy efficiency, etc.) are in fact nothing more than cost-cutting measures that boost its bottom line. Until Wal-Mart makes some hard choices itself—such as paying all its workers a living wage—nothing it does in the blogosphere or elsewhere is going to be very authentic.