In spite of his obvious Anti-Semitism, Irving was/is a prolific and to many, a well regarded author on the subject of World War 2. I hadn’t heard that he (finally) admitted his denial of the Holocaust was wrong. In spite of all this his books are well sourced and when it comes to military events of that war, well written.
"Yes, and besides that, how did you enjoy the play, Mrs. Lincoln?"
"Scum of the earth" is an appropriate metaphor for David Irving's ilk.
Of course, even scum has its useful qualities, for example in the manufacture of bio-fuels...
Oh, dear, did I say something insensitive?