It's not so much the judge got it wrong, it's the Canadian criminal justice system got it wrong.
We don't throw the book at criminals anymore. Violent crime like this case nets you a slap on the wrist, if that.
When the conservatives under Harper proposed changes like changing the sentencing guidelines so that a life sentence actually meant a life sentence, there were howls of outrage in the media and supposedly in the populace (not me). Of course, we don't have enough money to incarcerate all the criminals out there, but that's another issue.