The main problem, which you just repeated, is the perception he conducted a large number of investigations. He did not. he wrote up probably triple what he investigated or conducted.
Looking back, he was very careful to stay away from any Martially related statements. He always deferred to the actual practitioners.
Since Mr. Harding was part of numerous Bullshido investigations, his dishonesty throws a taint (albeit a mild one) on all of the investigations that he was involved with.