By your logic a woman couldn’t be raped because she got wet and had an orgasm. Getting an erection isn’t a conscious thing that men will by, like lifting an arm. Plenty of men also get physically abused by their girlfriends / wives, despite being physically stronger and technically able to overpower them. If you really cannot fathom how psychological pressure & abuse works then I am not sure where to even start. I got raped by my ex early in my life when I was sleeping. And yes, men can get a boner when asleep too. I woke up during the event, obviously confused, and just went with it, before falling asleep again. I only understood what even really happened much much later in life.