Revelation 2

20 Nevertheless, I have this against you: You tolerate that woman Jezebel, who calls herself a prophet. By her teaching she misleads my servants into sexual immorality and the eating of food sacrificed to idols. 
Sexual immorality often hurts because of violates the commitment so necessary to building up a relationship in Godly fashion. It can destroy families and churches because it destroys the integrity on which these relationships are built, thus God wants us to take no part in it even if our culture accepts it.