I have avoided this thread like the plague because I knew I would read something that would make me angry, but hey, my morbid curiosity overtook my sensibilities and here I am.
I come from a more diverse background than most folk, My family is VERY diverse and I am what is considered a 'mulatto' in many parts of the world.
I HATE when people identify African/Caribbean people by the colour of their skin, which is a stupid thing to do anyway. For example, my DD is mixed and many would call her a 'black girl' BUT SHE ISN'T!! Her skin tone is caramel if you want to apply an accurate colour to description to her, NOT BLACK! If someone identified her by calling her a 'black girl', I would be massively offended and they would hear about it. In mixed heritage people, it also fails to acknowledge their non African/Caribbean heritage.
Using black as an umbrella term to describe people of African/Caribbean heritage is offensive because it has been a way of making them an 'other' and alien social group by those who would wish to exploit them for generations. It also encourages an environment where African/Caribbean culture and heritage can be ignored to dehumanise the 'black man'. By calling someone a 'black man' instead of acknowledging his individual and more personal identifiers, you 'other' him.
People are not black and they are not white. I identify people by the continents, countries and cities they come from if I have to. But for the most part, I identify people by their names or characteristics. For example, 'that guy with the afro', or 'the lady from Kenya with the braids'. It isn't hard to do.
Because of the history of racial discrimination in this country and many others, calling someone a 'black man' is offensive to many who are educated enough to understand the connotations.
I am working class BTW.