They not only insulted the King but the heir to the throne as well. The king's anger is justified because they openly refused to give the king the honor he was due. Jesus directed this warning to the Jews of his day, both to convey how much God wanted them to share in the joy of his kingdom, but also to give a warning about the consequences of refusing his Son, their Messiah and Savior. The second part of the story focuses on those who had no claim on the king and who would never have considered getting such an invitation. But this invitation also contains a warning for those who refuse it or who approach the wedding feast unworthily.
Grace is a free gift, but it is also an awesome responsibility.
Costly grace is the gospel which must be sought again and again, the gift which must be asked for, the door at which a man must knock. Such grace is costly because it calls us to follow Jesus Christ. It is costly because it costs a man his life, and it is grace because it gives a man the only true life. God invites each of us to his banquet that we may share in his joy. Lord, may I always know the joy of living in your presence and grow in the hope of seeing you face to face in your everlasting kingdom.