In your personal opinion, which of the four McCullagh scenarios do you consider to be the most counterproductive to valid historical scholarship, and why?

In the essay “Bias in Historical Description, Interpretation, and Explanation” C. Behan McCullagh suggests there are four common ways in which historical writing might become biased. In your personal opinion, which of the four McCullagh scenarios do you consider to be the most counterproductive to valid historical scholarship, and why?