A small but growing number of defectors from the Islamic State are risking reprisals and imprisonment to speak out about their disillusionment with the extremist group. The Islamic State considers defectors as apostates, and most of the hundreds thought to have left the group have gone into hiding. But 58 defectors, nine of them from Western Europe and Australia, have gone public with their testimonies since last year, according to a report to be published Monday by the International Center for the Study for Radicalization at King’s College London.