Jeff,
True, holding yourself out as a CPA won't get you sued, but holding yourself out as a CPA and taking on an engagement where you don't have the necessary skills to effectively execute it not only will get you sued, but your license can be put in jeopardy for misrepresenting your expertise as a CPA; that's an ethical violation.
I think that is the point Mr. Mini is trying to make:
Holding out as a CGMA when you do not have the technical skills necessary to effectively perform the prescribed duties can be an potential ethics violation. So if someone gets the CGMA designation and an employer or client relies on that designation as a basis for hiring them for a job position or engagement, and if the CGMA has no experience in management accounting and they botch up an engagement or put their employer in danger of being sued as a result of their substandard work, not only can the CGMA be sued, but they can also get their CPA license suspended/revoked for misrepresenting their expertise and endangering the public as a result. That is why the AICPA Code of Conduct 501 is in place, to prevent things like this from happening.
A more common example: If your specialty as a CPA is in tax preparation and advisory, don't hold yourself out to be an auditor. Or if you want to venture out into auditing, get some CPE and some training/guidance under a CPA who specializes in auditing would be highly recommended (although the work experience requirement prior to licensing is supposed to mitigate such issues as this from occurring). If you hold yourself out as a auditor and you “wreck” the engagement, the client can not only sue you, but also file a complaint with the accountancy board which could bring several violations (negligence and false/misleading advertising are a few that comes to mind).
In short, Mr. Mini is very much on point with his concern of possible ethical ramifications of these new “CGMAs”. Be careful how you hold out using those letters.
AUD - 79
BEC - ?? 10/1/15 (Tentative)
REG - ?? 11/?/15
FAR - ?? Winter 2016