Whereas the AICPA Code of Responsibility actually incorporates the word objectivity (in addition to the word independence), the GAS GAGAS uses only the latter, but, in fact, either denotes the same concept, that objectivity is an essential professional obligation of accounting and auditing The mechanical or computational aspects of accounting are, by nature, purely objective and not inherently susceptible to subjective interpretation or application, in general principle. However, the actual practice of accounting and auditing leaves considerable room for subjective belief, such as where the professional must make an independent determination of what degree of truth may be presumed in the case of explanations, assurances, or characterizations unsupported by independent corroboration.

A professional applying a personal ethical perspective to a client's circumstances might very carefully and appropriately apply objective technical rules and codes while inappropriately allowing his personal beliefs and opinions about the client to influence his subjective determinations with respect...

Another possible temptation possibly associated with the substitution of personal ethical standards for professional standards is providing of "creative" assistance with respect to ensuring that assets, liabilities, and deductions are manipulated to conform to the characterization most beneficial to the client, particularly in the many ways that the expertise of the professional allows manipulations that are essentially undiscoverable by auditors. In general, the fundamental requirement to rely exclusively on objective standards merely ensures that professional accountants adhere to the spirit, and not just the letter of law.
References

AICPA Code of Professional Conduct Section 55 - Article IV -- Objectivity and Independence. Retrieved March 2, 2008, from the AICPA website, at http://www.aicpa.org/about/code/et_55.html

GAO (2008) Government Auditing Standards 2008 Revision.