Is It Really True That No One Is Harmed?

"The argument that certain actions are not wrong, provided they are performed by consenting adults and no one is harmed, disregards the fact that sin is primarily wrong against God and primarily affects the relationship between the sinner and God." - Millard Erickson (Christian Theology Second Edition)

Sin causes the sinner to run away from reality in an effort to avoid the real consequences of their sin.

The main consequence of sin is eternal death. We have eternal life with God in heaven when we turn from our sins and accept Christ as our Lord and Savior. When we turn away from God and embrace sin, God gives us what we want--eternal separation from Him. Eternal death.