History, Religion, Ignorance
The greatest injustice in history happened to the Jews. Jews found God and the ways to pray. They used music and singing to praise God. They designated a place, then a building, then buildings for worship. Christians and Muslims pray to the same God that the Jews found. They also built places for worship. There is music and singing in churches. So Jews should have been appreciated, since the other two religions originated from Judaism. Instead Jews got hate.