For the 14th year in a row, shareholders at oil giant ExxonMobil overwhelmingly shot down a proposal that would specifically prohibit discrimination based on sexual orientation and gender identity.

The proposal, sponsored by New York State Comptroller Thomas DiNapoli and brought before shareholders on Wednesday, asked ExxonMobil (XOM) to add wording to its Equal Employment Opportunity policy that would explicitly protect lesbian, gay, bisexual and transgender employees from discrimination.

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"Employment discrimination on the basis of sexual orientation and gender identity can diminish employee morale and productivity," the proposal stated. "ExxonMobil will enhance its competitive edge by joining the growing ranks of companies guaranteeing equal opportunity for all employees."

But opponents said the company already broadly prohibits discrimination of any kind, according to the proxy statement provided to shareholders ahead of the meeting. And shareholders ultimately voted 80% to 20% against the proposal on Wednesday.

"Based on these existing all-inclusive, zero-tolerance policies, the Board believes the proposal is unnecessary," according to comments from board members in the proxy statement. ExxonMobil declined to comment beyond what was said in the proxy statement.

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This decision puts ExxonMobil in the small pool of 12% of Fortune 500 companies that don't specifically ban discrimination based on sexual orientation in their Equal Employment Opportunity policies, according to the Human Rights Campaign.

And while the average Fortune 500 company received a "corporate equality" score of 54 out of 100 last year -- based on how LGBT-inclusive their policies are -- ExxonMobil received a negative 25, according to HRC's ratings. That's much lower than other major players in the oil industry, like BP (BP) and Chevron (CVX), which each received scores of at least 85.

"No company has proven itself a worse corporate citizen by betraying its LGBT employees time and again than ExxonMobil," HRC president Chad Griffin said in a statement. "By failing once more to do the right thing, ExxonMobil places itself firmly on the wrong side of history. Fair-minded consumers should take their business elsewhere."