If someone really belongs to the LORD and is living in sin, GOD will deal with them. "Take them to the woodshed", so to speak.
Proverbs 3: 11 & 12
11My son, despise not the chastening of the LORD; neither be weary of his correction:
12For whom the LORD loveth he correcteth; even as a father the son in whom he delighteth.
Dr Adrian Rogers preached a great message about this very subject.