The person who posted this video to youtube also put some scripture up to explain it.
Ibn Ishaq and al-Waqidi report that the prophet said the morning after the murder (of Kab Ibn al’Ashraf), “Kill any Jew you can lay your hands on.” (El beddayah wa alnihaya — Ibn Katheer — vol. 4 — in the chapter on killing Ka’ab bin al’Ashraf)
Omar Ibn al-Khatab said: “I heard the prophet of Allah saying: ‘I will cast Jews and Christians out of the peninsula and I won’t leave any one in it but Muslims.'” (Sunan Abu Dawud, vol. 2, No. 28, from the Muhaddith program)