That’s not true. I don’t know about Jefferson’s case, but not all slavery was the same. There are examples of slaves and masters genuinely falling in love, or masters treating slaves as members of their family and freeing them from the slavery. It’s withnessed by the salves descendants and the slaves themselves in books like Slave Narratives.
Furthermore, if the slave was the one who seduced the master, not because of fear, but because it would alow it to get into better position or social status, then it’s not rape. The same way it’s not rape when today’s people willingly marry and have sex with their partners because of their wealth.
I understand the slavery was an opressive situation where a lot of abuse happened, but generalising without evidence just blurrs the truth and weakens your argument. You would have made a much stronger case if you didn’t go into unsupported generalisation.