Because there may be an underlying political interest in maintaining the "official" position. For example, if anthropogenic climate change is "fact", and not ju

Because there may be an underlying political interest in maintaining the "official" position. For example, if anthropogenic climate change is "fact", and not just a theory, then legislation such as cap and trade may be easier to pass. Also, when people adopt an unfashionable or non-PC position they are more likely to experience ostracism and even persecution. That would seem to be a significant barrier to entry into these "opposing factions".