A total stranger can hurt us, but there is no hurt greater than that which comes from one we want to love us. When I was a boy I was hurt by other children who excluded me from their games. When I was a teenager there was no hurt greater than being laughed at. As an adult I was hurt by those who did not return my generosity. I mistakenly thought that if I was kind and nice to others they would be kind and nice to me.
Rejection is an excruciating form of pain.
If that doesn't work, Jesus says, take the matter to two or three others - presumably people close to you whom you can trust. If that doesn't work - let go of both the hurt and the one who is hurting you. Don't cling to the cancer. Jesus is quoted here as saying that if all else fails, treat the offending party like you would treat a Gentile, or a tax collector. Churches have used this passage as justification for the act of formal and judicial excommunication from the Faith Community.