Here's why:
* It trivializes slavery: Slavery was a horrific institution that caused immense suffering and death. Using the word "slave" in this context minimizes the brutality and dehumanization involved.
* It implies ownership of people: The sentence suggests that someone once owned another human being as property, which is morally reprehensible.
* It's likely to cause offense: This sentence would be deeply upsetting to anyone who understands the history of slavery and its lasting impact.
Instead of using this sentence, consider the context and try to express yourself in a way that is respectful and sensitive to the history of slavery.