I think the keyword is "indifference." While everybody miscalculates the CEO - unskilled pay ratio, the article is implying the indifference caused by "American cultural optimism" is what prevents us from changing it.
Let's say that American's perception of social mobility was found to be significantly skewed relative to that of other populations'. Would that show more or less indifference? You could argue that the 'American Dream' cultural thinking leads more Americans to believe that the poor can become rich and at the same time more passionate about ensuring that that is indeed the case. The fact that it blinds them to the reality does not imply that they don't care.