White Robinson and black Friday

Today in microeconomics we were talking about a two-men economy, with Friday and Robinson Crusoe as examples. On the wall was a picture of a white Robinson and a black Friday. Some of the examples given by the lecturer were a bit drastic, for example starving a person, which started a wave of semi-racial jokes. When the lecturer asked: "so, who in our economy should get no food", a voice from the crowd answered: "of course the black". This caused an interesting division: we were no longer students, we were white and black students.
You rarely hear Germans speaking about color, race (oops, pardon me using such a naughty word), or similar topics - a stigma from the WWII. The lecturer broke an unspoken taboo and it was interesting to watch the reactions. Some people were embarrassed, some laughed nervously, of course there were also those, who didn't react in any way (but only few of them were sitting in my corner of the lecture hall). I was wondering, how it was possible, that mature twenty-something students would make such a fuss after seeing a picture of a white and a black man.
I come to the conclusion that in Germany race (oops, I did it again) is still a very heated topic and despite the efforts of the '68-movement the past was not cut off completely. It is socially inappropriate to vent on race-issues (eg. through comedy, satire, jokes etc...) and many people seem not to know how to react when a race-related topic is brought up. A lot of fuss is made when somebody says something "inappropriate" and I am not sure if that's the best reaction.
From what I have noticed, in America race seems also a big issue. One of my black-American friends was often saying that there are only two races in America: blacks and whites, and all the rest is siding either with one or the other. I think it a bit of an exaggeration, but he made it quite clear, that America is not as color-blind as it would like to be.
In Poland we hate other Poles, or gypsies, or Jews, but there are probably too few blacks to collectively hate them.
Interesting enough, when you travel through Chinese villages, people do not care whether you are white, or black, or brown, or purple, or green, or silver - sure, they will be curious, but they will welcome you no matter what color you are. I guess they have seen to few green people to hate them.