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At the time of the parable, the Jews and the Gentiles had been in enmity for years. The differences between them were cultural and religious. The Israelites, who were not carried away by the Assyrians, intermarried with other resettled people in that area and a new race emerged (the Samaritans). Some of the Jews that returned from exile viewed the Samaritans as unclean (having intermarried the Gentiles) and renegades of the faith (Samaritans adopted only the Pentateuch into their canon and worshiped on Mount Gerizim instead of Mount Zion). This was the cultural setting of the parable.
This problem of cultural and religious differences was so deep-seated that Jesus rebuked the religious Jews in Mark 7, even Saul (before he became Paul) thought he was doing God a favour by exterminating people who were not one of their own. Paul, then elaborated on the grace of God in reconciling the Jews and the Gentiles in his various letters (Rom 3, Rom 11, Gal 2).
The ploy by the Devil in playing up cultural and racial differences was evident early on and is still deployed today.
The grace of God overcame by God reconciling people to Himself and reconciling people to one another.