You are one fucking retard, viagra does NOT give you an automatic erection against your own will. It only helps people with erection disfunction and gives a slightly bigger erection on normal people.
So the women waited around until that guy had a morning erection and then raped him before he went limp?
It is NOT possible to rape a man in the conventional sense because if a man totally doesn't want it, you can't make him stiff. Erections can only happen when the guy is in a receptive state of mind. If a guy is being beaten up and tortured no amount of forced sexual 'stimulation' will give him a boner (unless he's into S&M). Especially not at gunpoint because when you are scared, the blood in drawn away from the extremities of the body, so even if you had an erection before it will fold pretty quickly if someone threatens your life with a gun.