Lawyers' ability to respond to online criticism is sharply limited by both confidentiality and prudential concerns according to the ABA's newly issued Formal Opinion. The opinion largely tracks the opinions of bar associations, and official ethics committees.
One of the closer questions is what constitutes a controversy between attorney and client, relieves the lawyer of certain strictures of confidentiality under RPC 1.6. The ABA Committee opines:
even if an online posting rose to the level of a controversy between lawyer and client, a public response is not reasonably necessary or contemplated by Rule 1.6(b) in order for the lawyer to establish a claim or defense on behalf of the lawyer in a controversy between the lawyer and the client. Comment  to Rule 1.6 supports this reading explaining, “Paragraph (b) permits disclosure only to the extent the lawyer reasonably believes the disclosure is necessary to accomplish one of the purposes stated.”
It is, however, a noteworthy suggestion that
A lawyer may request that the host of the website or search engine remove the post. This may be particularly effective if the post was made by someone other than a client. If the post was made by someone pretending to be a client, but who is not, the lawyer may inform the host of the website or search engine of that fact. In making a request to remove the post, unless the client consents to disclosure, the lawyer may not disclose any information that relates to a client’s representation or that could reasonably lead to the discovery of confidential information by another, but may state that the post is not accurate or that the lawyer has not represented the poster if that is the case.
Lawyers are regularly targets of online criticism and negative reviews. Model Rule of Professional Conduct 1.6(a) prohibits lawyers from disclosing information relating to any client’s representation or information that could reasonably lead to the discovery of confidential information by another. A negative online review, alone, does not meet the requirements of permissible disclosure in self-defense under Model Rule 1.6(b)(5) and, even if it did, an online response that discloses information relating to a client’s representation or that would lead to discovery of confidential information would exceed any disclosure permitted under the Rule. As a best practice, lawyers should consider not responding to a negative post or review, because doing so may draw more attention to it and invite further response from an already unhappy critic. Lawyers may request that the website or search engine host remove the information. Lawyers who choose to respond online must not disclose information that relates to a client matter, or that could reasonably lead to the discovery of confidential information by another, in the response. Lawyers may post an invitation to contact the lawyer privately to resolve the matter. Another permissible online response would be to indicate that professional considerations preclude a response.