He's abandoned the values of the West and is fighting for our enemy (ISIL or any other radical Islamic terrorist group bent on our destruction) who are hell-bent on converting everyone to fundamentalist Islam to live in their repressive caliphate. He is a trader, who is threatening our way of life. He can no longer be considered a British citizen. 
The moors murderers was one twisted man and his twisted girlfriend who were not threatening to exterminate the western world and make us live according to their view of Islam. Not the same thing.
And yes, Bibeau can be included in with this British terrorist. They are at war with the West and I don't give a flying monkey where they were born.