Content warning: this post discusses rape and quotes text advocating for it.

Given the basically unlimited power an enslaver has over the people enslaved there's no situation where consent can or should reasonably be assumed. Even people who have a genuine mutual attraction to one another are not immune to the power dynamic. We are speaking of rape here; however technical we want to make it we should not forget that

Most white enslavers did not consider the people they enslaved to be non-human so, by and large, the question simply wouldn't occur to them. They were raping people they believed to be humans, if of a massively inferior order. Polygenism, the belief that blacks were a species distinct from whites, is a strictly minority position within the US. Few thinkers argue it and fewer still receive warm receptions when they do. The chief objection, for most enslavers, is strictly Biblical: the Good Book only has the one Adam rather than a bunch of separate creations. The major exception in the usual proslavery canon (the kinds of books enslavers are more likely to read, rather than something like an anthropology text) is Josiah Nott, who probably didn't help himself by being fairly condescending to divines who objected to his ideas in the same works where he promoted them.

When they discuss this kind of thing in public, which is rare given contemporary mores, enslavers tend to argue that the rape of enslaved women is a good thing. There's no gentle way to put this, so let me just quote one of them:

Negro slavery has a further effect on the character of the white woman, which should commend the institution to all who love the white race more than they do the negro. It is a shield to the virtue of the white woman.

So long as man is lewd, woman will be his victim. Those who are forced to occupy a menial position have ever been, will ever be most tempted, least protected: this is one of the evils of slavery; it attends all who are in that abject condition from the beautiful Circassian to the sable daughter of Africa. While we admit the selfishness of the sentiment, we are free to declare, we love the white woman so much, we would save her even at the sacrifice of the negro: would throw around her every shield, keep her out of the way of temptation.

This is from Benjamin Franklin Stringfellow's Negro-Slavery, No Evil, a pamphlet he wrote on behalf of a paramilitary group he involved himself with for the project of imposing slavery on Kansas. He specifically intended it as a document to be widely circulated as a defense of what they intended to do. Though he wrote it on his own, he presented it to the group and they voted their approval for it to be printed and released with the name of their association attached.

Stringfellow is careful not to say that rape is a good thing in general, but he admits that slavery is good in part because it supposedly spares white women from being raped. So far as I've read, that's about as close as one can get to an expression of discomfort by an enslaving man on the subject. For most of them, this is just a matter of course. There was an established trade in "fancy" slaves, women sold specifically to be raped. They would have other duties too, but their selling points came down to their sexual appeal to white men.