The king was angry because he chooses guests and invited them for the marriage feast of his son but they ignored his invitation.

The point Jesus was making is that the kingdom of God was for the children of israel only the choosen tribe,but because they ignored his call and invitation he was telling them how the gentiles are getting chance of attending the kings son  wedding.non israel by tribe was not allowed to enter in kingdom of heaven but because of the israel rejected to obey the lows of the king (Jesus) and to follow him we became spiritual israel and have visa to enter in the wedding throw blood of Jesus christ the son of almighty God.