I would highly recommend looking into the works of David Irving, who was once considered a world class historian before covering the wrong topics ended his career. The records of the various court cases in Canada where he was represented by the late Doug Christie regarding his "hate speech" and other offenses are excellent primary sources on the topic with expert testimony and the only case I am aware of where 'eye-witness' accounts were allowed to be cross-examined.

There are several books written by him, as well as a few hundred copies of a book that is a compilation of these court records floating around.