Kate Chopin was the daughter of a rich French-Creole woman, and later became the wife of Oscar Chopin, a French-Creole man with whom he later on moved to Louisiana.
Fully acquainted with the history of Creole Louisiana, Kate Chopin based the problem of her story "Desiree's Baby" on the Louisiana Civil Codes of 1808 and 1825 which made mixed-race marriages illegal to the point of cancelling out any rights of inheritance to children born of those marriages.
We know that Armand moved to Louisiana with his father at the age of eight from France, and that his mother supposedly never moved to Louisiana because she loved France too much. This is not the case. The reality is that Madame Aubignys was black, and the only way for Armand's father to marry her legally would have been if they married in France. If Madame Aubignys had moved to Louisiana, her son's status as an heir would have been in jeopardy.
As can be seen the historical context of the story shows the clear social differences among blacks and whites in 19th century Louisiana; so strictly delineated were the two races that the sole mixing of the would have been considered illegal. When Armand accuses Desiree of being black, he is insulting her not only racially, but socially, and legally. Their child is no longer a "valid" child, and for this reason, Armand abandons them both.