It occurred to me, from what you guys point out, is that it gives the robot who stabs him an MO. Yet that would be our perception, that he had sex with it in a non consensual sense of ....well
he didn't ask probably....but this would be a reflection of human mores.
Now if Ex Machina is a story where robots are made to act like humans; it loses much purpose. It is saying that it isn't a case of AI pretending to be human but mirroring human behaviour because it has been programmed to do so. A lot of evidence is there to support that conclusion, like the early statement that big data has been used to create the AI sentience. This seems to fit a lot of the "facts" of the film but it reduces the story to one consisting of humans and robots acting exactly like humans (or more accurately actors playing robots acting as humans). You hardly need the AI angle at all, except for a little juxtaposition....except the female robot avenging abuse in exactly the way a female human would says nothing new whilst purporting to say a lot.
My head hurts.