Most Professors are arrogant, opinionated tyrants who cannot tolerate disrespect from students, especially undergraduate students. You don’t need to postulate racism here to explain her reaction to your criticism, just intellectual pomposity and intolerance.
For the record, I thought the dildo joke was crude, but actually quite funny, and I think it is admirable that so many slave families managed to maintain their family structure in spite of the institution of slavery, and all the oppression that implies. I don’t understand why this made you so mad.
Seems to me that we should be proud of that family loyalty triumphing in spite of the suffering, of being owned by racists, and treated like cattle. I don’t think a racist would have pointed out the triumphant humanity of Slaves under slavery.