Let's remember this was the 1940's and referring to black people as niggers was the norm.
It was still common in the 60's as I can remember buying a polo shirt from BHS in Brighton that the colour was labelled as 'Nigger Brown'.
Again in the 60's we had a weekly 'To Death us do Part' where black folk were referred to as 'Coons'. Other TV shows such as 'Love thy Neighbour' and the 'Black and White Minstrel Show' were standard viewing.
It's history and can't be whitewashed [Sic].