See, to me this is very simple. This single act, which did not even have to be proven in a court of law (because he pleaded no contest) is inconsistent with him living among us.
There are violent acts that can get you arrested that have poor predictive value-bar fights, for example. But clubbing a strange woman so you can drag her into the woods is not one of them.
This act, or worse, was inevitably going to be repeated (and repeated) until he was dead or incarcerated.
For that matter, if he were incarcerated in a normal American prison, such acts would inevitably be repeated on weak or non-violent inmates, or prison staff.
The best solution for someone who pleads no contest to clubbing a woman so he can drag her into the woods is that he be killed. If that were done in this case, this little girl would still be alive.
Failing that, a person like this should be isolated from society in a secure location, where he can live with others of his own kind and do whatever they would do to each other-without societal intervention.