It is professional misconduct for a lawyer to:
(a) violate or attempt to violate the Rules of Professional Conduct, knowingly assist or induce another to do so, or do so through the acts of another;
(b) commit a criminal act that reflects adversely on the lawyer's honesty, trustworthiness or fitness as a lawyer in other respects;
(c) engage in conduct involving dishonesty, fraud, deceit or misrepresentation;
(d) engage in conduct that is prejudicial to the administration of justice;
(e) state or imply an ability to influence improperly a government agency or official or to achieve results by means that violate the Rules of Professional Conduct or other law; or
(f) knowingly assist a judge or judicial officer in conduct that is a violation of applicable rules of judicial conduct or other law.
 A lawyer who, in the course of representing a client, knowingly manifests by words or conduct, bias or prejudice based upon race, sex, religion, national origin, disability, age, sexual orientation or socioeconomic status, violates paragraph (d) when such actions are prejudicial to the administration of justice. Legitimate advocacy respecting the foregoing factors does not violate paragraph (d). A trial judge's finding that peremptory challenges were exercised on a discriminatory basis does not alone establish a violation of this rule.
Thomas D., and Ronald D. Rotunda, eds. 2005 Selected Standards on
Who defines "legitimate advocacy"? Since this is a rule on reporting, this initial assessment is made by whomever chooses to report an attorney for allegedly violating the rule. The state licensing board would then, I presume, decide whether the accused attorney's advocacy falls within "legitimate" grounds.
I must be skeptical of how legitimate is defined, by whomever defines it, because I fear that it is too easily definable narrowly to exclude advocacy of viewpoints not socially acceptable. While I can easily foresee our Solicitor General's advocacy against gay marriage being considered legitimate by state authorities, I can just as easily see how advocacy of attorneys for the Catholic Church or attorneys for associations with Catholic affiliation may not be considered legitimate advocacy. Yes?
Upon my first reflection, I too quickly thought the "legitimate advocacy" disclaimer eviscerated the rule, but upon further reflection my assessment has changed. I see now how the disclaimer may be used to enforce the rule discriminately.