To all of the people jumping down the throat of correlation topics, you cannot deny the character differences derived from penis size. While there is significantly little study done on the matter, I'm sure guys with bigger tools tend to be more confident. If this confidence spread to personal image, and some guy could be confident enough to have long hair, there may be a correlation.
Chances are, probably not.
But there might be, and simply saying, "there is no correlation. Never!" is absurd, because, there will be correlations.
And mentioning, "if I cut my hair, does my dick shrink?" is just showing your ignorance on the matter. The question is more akin to "Are guys more likely to have long hair also more likely to have a larger tool?"