I've been in those situations myself many times, being a half-beta male that isn't handsome enough to the point that women will submit to my urges at any time.
Believe me, when you've spent a whole day with a girl, a whole evening where she passionately made out with you, grabbed your crotch a few times, told you that she wanted you so bad, only to be told in her bed, so close to actual sex: "Sorry, I'm not in the mood anymore."
This is hard to get yourself together, insanely hard. Any guy will try to push it forward, which is what I did, and most of the time, the girl caved in... .... You're going to tell me I'm a rapist now I guess?
But seriously though, in the situation described above, there is little room for rational thought and 'doing the right thing' in that moment.