Of course you're right, the rapist unfamiliar with Ukemi would almost certainly end up with a broken wrist or neck!

What Aikido does offer though is the practice of remaining calm under stressful situations, which I think is useful whether yer facing a shit day at work, a rapist, or the body-armoured forces of the state.

Being able to choose to gouge out the eyes of any of the above is always preferable to doing so in a blind panic (no pun intended).