(Please read the Scripture passage before reading the homily.)
How am I supposed to treat someone as a Gentile or as a tax collector? Jesus ate with tax collectors and sinners. He also cured the daughter of a Canaanite women.
Excluding someone from the community is a drastic step. An animal that is pushed outside the herd or flock and made to be alone is an animal in deep danger from its enemies. A person excluded from the Christian community is likewise in great danger. So likewise are all the Gentiles and tax collectors in great danger, which is why we need to pray for those who are not included in the Christian community.
We do this, not because we are better than they, but because they are facing great danger without the safety of the community. Our prayer, then, is to share the safety the community gives us with those who are lacking this safety.
So if we are to treat some people as Gentiles or tax collectors, then we are to pray that we can share with them the safety we have.
The Church has the authority of Christ to bind and loose. Peter has the added authority of the keys. We, as Church and not as individuals, have power to bind and loose. We have to do all we can to bind people to the Church and to loosen them of their sins and danger.
Christ is always present when the Church gathers.