The adjective "social" implies that the verb or noun to which it is applied is somehow more communicative, cooperative, and moderated by contact with human beings, than if it were omitted. That is, it implies that larger society has played some role in defining the idea or the principle. For instance terms like social realism, social justice, social constructivism, social psychology and social capital imply that there is some social process is involved or considered that is not there in regular, "non-social", realism, justice, constructivism, psychology, or capital.
It is sometimes applied in right-wing politics as a pejorative, that is, to imply that the idea or concept is inferior for having undergone this social process, which might be seen to be compromising. As if to validate this perception, in left-wing politics the adjective "social" is often taken to mean, simply, "good". What is not social is thus defined to be "bad" or at least to be investigated carefully before being accepted as truth or worthy of trust.
For these reasons, those seeking to avoid association with the left-right political debates often seek to label their work with phrases that do not include the word "social". An example is quasi-empiricism in mathematics which is sometimes labelled social constructivism by those who see it as an unwarranted intrusion of social considerations in mathematical practice, which is supposed to be "objective" and "above" social concerns.
See also: racial, global, political, international, society