jockosjungle:
it would be hard to portray black people as any color other than pure black
It's quite easy to draw black or asian people using just black and white, it's well-accepted now that people can tell a race from smaller pointers such as hair style or shape of mouth, nose and eyes.
In the 1970s and early 80s it was still acceptable to show a negro or asian character by drawing diagonal 'shade lines' across their skin, but this is not seen as acceptable now.
You're right though, jocksojungle, Hergé was just drawing in the style of the time.
Going back to the middle of the 20th century, it was acceptable to draw a black person with big lips, large white eyes and their skin completely black because that was cartooning, the same way you might show a person of Jewish origin with a large nose. It's not necessarily racially accurate, but the point of cartooning is/was to make an almost grotesque portrayal of a character whether they were black, white or whatever.
If you look at most of Hergé's black characters at face value, they are not racist.
What is racist is the history of racism that often went hand-in-hand with derogatory cartoons and therefore often made that 'rubber-lipped' figure a racist depiction. The Nazis made strong use of cartoon stereotypes to depict the, in their view, 'evil' nature of Jews and the 'stupidity' of any minority race.
Robert Crumb's
Angelfood McSpade can be seen as
very offensive, until you realise he's taking the mickey out of cartoon racism - though it is difficult to read, but he plays very strongly on that black cartoon stereotype.
In some ways, today it's gone almost too far the other way. When I drew a totem-pole of three children standing on each others' shoulders, one black, one asian and one white I decided to put the black child at the top so no one could accuse me of putting him at the bottom of the heap. It still got strongly criticised, as I'd put the white child on the bottom (almost reverse racism!) and was told I was showing that black people needed to be held up and helped by white people! I encounter this quite a bit, and in all my children's illustrations have to have a very balanced scattering of races - which is fine, but sometimes things go too far.
After that very long ramble - I'm basically saying that Hergé's 'black cartoons' are not in themselves, racist, they're just cartoons - but an unfortunate history attaches itself to them.