if he would have been convicted of murder of 5 people then probably nobody would complain.
but he is not and there are no people dead. (and as far as I remember even one of the people who should have been killed spoke out in favor if him)

and even if we assume the chat is real and from him the sentence is not justified, is it? actual murderers have gotten way less. 

It’s been many years that I researched the case more - I need to refresh it - but just from looking at the crimes he is convicted for the sentence is a no-go. (esp. in comparison to other sentences of similar crimes)