There comes a point when what should be a normal distribution curve becomes so distorted away from 'normal' that it can no longer be described that way and is showing a trend which is not neutral.The issue fans have with referees is the incredible amount of inconsistency around decisions that ironically is consistently applied to the benefit of certain teams.
And when we're so regularly on the wrong side of that ledger it is no surprise when integrity starts to be called into question.