When the government was elected it promised to be "tough on crime, tough on the causes of crime" and it seems their promise has been carried out but they forgot to build enough prisons to house these criminals!
I believe in a short, sharp, harsh shock. A short but hard prison sentence, along with re-training and counselling should put most people back on the right path. Persistent offenders should get longer, tougher sentences and be made to do some sort of useful work.
Sex offenders should ALWAYS be locked up. As I understand it though, this chap had downloaded child porn but was not convicted of any assaults.