I think this short story teaches how destructive prejudice can be. Armand was deeply in love with Desiree, telling her that her uncertain ethinic roots did not make any difference to him. Ah, but he did not consider that she might have some Black blood in her. When their baby is born and the child is obviously of mixed race, he automatically assumes that it is from HER side, not his. After all, he is a blueblood, an aristocrat. His racial prejudices are so strong and his pridefulness in his own bloodlines so deep, that he lets the child, the symbol of race, destroy what is beautiful, his love for Desiree.
The great irony of the story is that the mixed race comes from HIS family, not hers. So in the end, he loses everything; his wife, his baby and his cultural pride.
Another lesson we can learn from this story is that we sometimes tend to think we are more tolerant or accepting than we actually are.
Armand is an example of someone who appears to be very accepting of Desiree's "obscure origin." However, he is seemingly only thinking about her lack of a family name and not considering her possibly mixed bloodline. He is not concerned about her being adopted because he loves her so much, and in that timeframe when name was so important to families and bloodlines, he is showing an acceptance that is uncommon. However, it does not occur to him to question her ethnic background because she appears to be white.
It is not until their child shows the traits of African American heritage that he blames this on Desiree's bloodline and his intolerance toward her is shown. He has always been intolerant towards Blacks, as we see in the way he treats his slaves. But, his ability to "accept" his wife and her questionable heritage goes out the door as soon as his child exhibits the traits of "the race that is cursed with the brand of slavery.”