Jesus gives the parable in response to a Beelzebul controversy. Jesus denied the Pharisees' claim to be children of Abraham in no uncertain terms. This helps to elucidate the use of this expression by Jesus' enemies and Jesus' response in the Parable of the Empty House. The sides had been clearly drawn in this bitter controversy. Others apparently refusing to take sides, chose to remain neutral.
Neutrality is impossible.
After the Exile, Israel had abandoned idolatry, pledging allegiance to the Torah. The preaching of John the Baptist and Jesus had produced momentary religious excitement. But repentance that was not followed by submission to God's Rule produced only temporary results. The majority of the Jewish nation became prey to even greater Satanic domination than they had experienced before the Exile. They finally crucified the Lord of the Kingdom.