Here is another passage that means a lot to me right now:
He who practices deceit shall not dwell within my house; He who speaks falsehood shall not maintain his position before me. (Psalm 101:7 NASB)
As a father of seven, I have to take seriously my responsibility to make sure my house is a domain of truth. I cannot welcome into my home anyone who would practice deceit or spread lies. If I were to violate that principle, I would be indicating to my wife and children that such influences are acceptable.
So, while severing familial ties might be painful, I don't want my acceptance of a liar to cause my loved ones to follow in his or her deceitful footsteps. Sometimes we have to do painful things to maintain integrity and holiness.