World War II was a watershed for anthropology both here in the US and for anthropology in the European colonial powers. How each reacted, and how individuals from the different traditions reacted to the wartime experience and the post war environment is a fascinating story and chapter in the history of anthropology as an institution and a culture.
While we, as anthropologists, advocate and believe that we can be both "participants" and "observers," the truth is we can never separate the two roles like our physical and biological science colleagues can. We will always be both, even when we attempt to dehumanize our "participant" role to become "more" objective. It is this fact alone which makes "professional" ethics an important and extremely complex issue in my opinion.
For example, the choice to not participate with the military in such areas as human terrain analysis is an individual moral and ethical choice. But is not a collective (professional) excuse nor escape from the consequences of the choice since collective is made up of the range of individual choices.
As a profession, for example, we have no moral right to criticize the actions of others (outsiders) who could have benefited from an anthropological input but were denied that input because some members objected to their colleagues working with the particular group or in a particular situation.
The profession must take a stand on what is ethically acceptable behavior of its members and which is the demarcation between Us (those we speak for i.e. the profession) and Others (those we do not speak for nor represent). The role of the profession is to define and mediate the limits of a member's acceptable behavior as it applies to its unique jurisdictional claim over a member's public behavior as it reflects on the profession and membership.as a whole.
A professional organization is by its very structure both a social/economic institution representing a group of specially trained individuals; and is the intermediary between the professional practitioner and the general public. In the role of intermediary, it sets ground rules for the interaction and, in return, receives (formally or informally) the right to administer those rules from the governing public authority. It is authorized to be self-governing as these rules apply to its official members. But it also limits the professional organizations authority over its members. And this is the problem we face in our organization and structure as "professional" anthropologists.