This almost sounds like a greek tragedy, or something Shakespeare would come up with.
It's horrible all the way around. Horrifying and sad.
Had the rapist been a complete stranger, or a teacher or really any other adult; I don't think there would be such an outcry. It doesn't make it right, don't get me wrong, but most people would be sympathetic with a father's rage and wish for revenge.
The person I feel really contributed to this whole scenario is the wife. Had she not bailed the son out, this probably would not have happened. Why would she get him out of jail after doing something so horrible. Given the age difference, I would have expected this little girl to be shared by the two of them. But now I wonder. Would she have so easily gotten him out of jail had this little girl been her own?
Even so, she had a responsibility to her step-daughter, especially since she is so young and could not defend herself.
I honestly don't know how I feel about this other than saddened, sickened, and deeply torn.