This sounds like a textbook case of a speed limit being deliberately set too low, and resulting consequences.  Speed limits need to take into account the natural tendencies of traffic, or they are counterproductive, as in this case.  When 85% of the population realizes the speed limit is too low, and drives according to road conditions, ignoring the absurdly low limit, and a small number of drivers steadfastly stay at or under the number on the sign, you are going to have confrontations and accidents.  A spot like this should immediately have an 85th percentile study done, and raise the limit to something people are willing to obey in greater numbers.

In cases like this, whether the outlier is the one speeding, or the one not speeding, the outlier is the real problem.