Complex sentence: Two young adults named Abdullah Hashem and Joseph McGowen were welcomed in the seminar and were allowed to take video of it, but they believe the video they took is evidence that the Raelian Movement is a cult which should disband.
Split into simpler sentences: Two young adults named Abdullah Hashem and Joseph McGowen were welcomed in the seminar and got permission to videotape it. They believe the footage they took is evidence that the Raelian Movement is a cult which should disband.