It is wrong to have non consensual sex.
Brian and Barbara are lying on Brian's bed fooling around after having a lot to drink, and Brian notices Barbara has just passed out.
Brian wants to have sex.
Brian waits until morning when Barbara wakes up before asking for sex.
Brian has sex with Barbara while she's passed out, figuring she won't mind.
Barbara considers Brian a gentleman and consents, and the two have a great time.
Barbara gets pregnant, and Brian is on the hook for both child support and rape charges.