In the context of the great works he's produced and the messages he's conveyed, those words are a stinking extract, but not typical Roald Dahl, a writer of many literary masterpieces with loving messages. Sadly, such attitudes are a reflection of his time more than of him. You can find equally disturbing quotes from almost every great writers of past generations, be it William Shakespeare, Hellen Keller, Joseph Conrad, or O. Henry. That's just the ugly truth.
I am grateful that great writer of loving literary masterpieces, Roald Dahl, risked his life and bravely fought against the vile and evil Nazis who brutally wiped out entire branches of my Jewish relatives in Germany, whatever words he may have carelessly uttered in an off moment. Action makes a difference. A vast difference. Action, not carefully enunciated politically-correct words (worthy as such words may be), action defeated Hitler and the Nazis. With his action, as a fighter pilot, Roald Dahl contibuted greatly to defeating the Nazis, shooting down Nazi planes at great risk to his life. That means more to me than a few carelessly uttered words.
