Jesus sand 'But if thy brother shall offend against thee, go, and rebuke him between thee and him alone. If he shall hear thee, thou shalt gain thy brother.' Matthew 18. 15
Many fear today to say anything when they see another sinning. And yet it is clear from Christ's words that we have a duty to help our brethren who go astray. Help bring them back to the path with charity; it is to their good – and your own.