He is allowing someone to diminish the voices of those who have actually suffered rape and need justice.
He absolutely isn't. Many crimes like this rely on two opposing testimonies - what he said happened, and what she said happened. Even when an actual assault occurs it's very difficult to prove anything. Suing her for libel could absolutely discourage genuine rape victims from stepping forward.
He's not required to, no. It's his choice. And what is so twisted about it? Genuine rape victims have been ignored and under-represented for, well, probably forever. That is twisted. He has the choice of what he does here, many don't. He exercised that choice.
He absolutely isn't. Many crimes like this rely on two opposing testimonies - what he said happened, and what she said happened. Even when an actual assault occurs it's very difficult to prove anything. Suing her for libel could absolutely discourage genuine rape victims from stepping forward.