No, the problem is your interpretation of it. You're right, it's absurd to think that drunkenness is a defence against an accusation of rape. It's absurd if you attack someone in the street, and it's absurd if you're alone in a room with an equally drunk person. It's even absurd to believe that a situation could arise where people are sufficiently drunk that they can't give informed consent but are still able to initiate sex. Ted believes absurd things.