It all goes back to the violent squabbles which were an integral part of life in and around Medina when the increasingly powerful Mohammed arrived there in 622.
A mishmash of Jewish believers - some heretical in the extreme - were scattered around in at least twenty identifiable groups.
In the politics of the day, it was no great surprise that alliances switched and changed resulting in a number of occasions Jewish groups were against Mohammed - and paid a dreadful price for having been so.
Opposition to Mohammed was clearly 'not to be tolerated' and the roots of Islamic hatreds are certainly to be found there.