15 years for trying to kill an MP

Islamic extremist Roshonara Choudhry was sentenced to a minimum of 15 years in jail for attempting to kill her MP Stephen Timms, apparently as a result of watching videos on the internet.
Now I think this is an appropriate sentence, but it does beg the question of why a number of murders recently have received a minimum of a mere five years or so.

The judge only got one thing wrong! Those who shouted slogans in court about the Judge should have been held for Contempt of Court.