The problem of 'thick in status, thin in content' in Beauchamp and Childress' principlism

For many, Thomas Beauchamp and James Childress have elaborated moral reasoning by using the four principles whereby all substantive problems of medical ethics (and of ethics more generally) can be properly analysed and cogent philosophical solutions for the problems can be found. It seems that their 'principlism' gets updated, with better features being added during the course of the six editions of Principles of Biomedical Ethics. Nonetheless, Beauchamp and Childress seem to have been losing their way when it comes to the common-morality justification, which is the epistemological (and perhaps metaphysical) backbone of their method, and this is shown more vividly in their most recent (2009) edition of Principles of Biomedical Ethics. The author points out what he calls the problem of 'thick in status, thin in content' in principlism. The problem exists because principlism cannot adequately explain how the prescriptive sense of common morality it supports is consistent with the existence of what Beauchamp and Childress call the 'legitimate moral diversity in the world'. Because of this problem, first, the practical end that principlism allegedly accomplishes (ie, providing practical moral guidelines in a relatively 'thick' content, based on common morality) is frustrated, and, second, principlism makes itself the method of common morality de jure and of moral pluralism de facto.