In a long post on various matters, Razib Kahn asserts that people "follow the views of their social milieu, no matter their actions":
You follow the positions and views of your social and cultural milieu because it is a cognitively cheap and convenient way to go. Logical thought is energetically taxing. The changes of the milieu’s opinions though can occur very rapidly (at least on the cultural time-scale). As those changes result in a flip, your own rational faculties simply re-write the past accordingly. Inter-temporal cognitive dissonance is minimized, because people have a bias in attributing their views and opinions to their own conscious and rational faculties.The social science strongly indicates that the heuristic "believe what your peers believe" is the primary factor driving most opinion. So you always need to be careful about taking the self-serving rationales of the individuals at the heart of the phenomenon at face value.