Do you understand the meaning of the term Muslim?

When Muslims say all the prophets were Muslims, people react like we're speaking of a religious affiliation. Muslim does not necessarily denote a religious affiliation, it means one who submits to the will of God. If you believe that Moses, Jesus, David, Solomon, etc. submitted themselves to the will of God, that makes them Muslims. People who follow Islam today are called Muslims, because we are submitting to the will of God by following his religion.