Here are my thoughts, sorry if this is repeating anything anybody else has said, I haven't yet read the thread, just wanted to reply to the OP. Clearly the African guy doesn't know what he was talking about. Even IF he couldn't see that many Black/White biracial people in America have lived as Blacks, been treated as Blacks and think of ourselves as Black, especially if we have evident African admixture, you were most definitely entitled to speak on that question becuase I believe it required two point of views. That of the darker Black woman and that of biracial, multiracial, and non-Black women. Now I personally would have listened especially closely to the opinion of the darker Black woman, just becuase I have found the people who experience the prejudice or feel the jealousy may know more about it than the people who they are supposed to be jealous of. It's human nature. It's kind of what has been happening on this board, we have had some racial topics recently pertaining to how discriminated against Black people are in our society and it's not that White members opinions aren't valid but they aren't the ones who would know the most about it usually.
There was a similiar question on a mixed race forum I belong to that asked "Do Black Men prefer Lighter skinned or Mixed race women over darker skinned Black women?" I felt completely entitled to answer but I fully admitted all I could add was inconclusive becuase it was from the point of view of the supposed preferred group. I haven't really ever had a problem getting a Black boyfriend but that's inconclusive becuase it doesn't mean Black men prefer me to darker skinned Black women. It did add some weight to "Yes Black men prefer lighter skinned women" if only becuase I haven't had hardly any experiences where a Black boy dissed me (and when they did it was usually for someone yet lighter than me or he preferred White women), and even less where they have dissed me for someone darker than me. The group that could really answer that question of yours and the question I answered would be darker Black women. They would be the ones most likely to notice any prejudice against them.
And the term mutt indicates this guy had some prejudice towards mixed race people. Some mixed people use it endearingly about themselves (President Obama has) but when outsiders use it (like Kanye West referring to the preponderance of light and bright dancers in music videos and how he uses them to sell his music despite thinking of them as animals) it usually means whatever is going to come out of their mouths next is not flattering for Multiracial people. Yes, people we have officially reached that point where Mixed Race is becoming legitimately a group/race, you can tell when people start to insult us. You know you have arrived when you have haters.