Your point is utterly ridiculous though and displays a lack of empathy on your part. As well as perhaps reading comprehension.
Consider - when he committed this crime 15 years ago he did indeed behave despicably (not knowing the full extent of the case it's hard to judge further). But e you are saying that in 15 years this man could not change. The idea of jail is to rehabilitate. To learn the error of his ways. Do you think it's possible that, in 15 years of self examination and thinking about your crimes that he might develop a greater sense of empathy? Should he be allowed to grow as a person at all?
Wait no, he's a scumbag and so is not entitled to change as a person or have rational thoughts, right? Would certainly make killing him a lot easier if it was so black and white (for want of a better term...)
He fucking argues that he didn't actually kill someone when he slit someone's throat. He has not changed, he thinks his sentence is an injustice. His argument is actually insulting as he tries to place himself with other people who are unjustly imprisoned when he completely deserves to be locked away. He is not rehabilitated if he is arguing semantics when he slit someones throat.