Rationalizing sin is what we do best, isn't it? Well, it is one of the best weapons the devil uses to convince us that there's nothing wrong with wrong things; that sin isn't sin and that there are no consequences other than feeling bad for a few seconds.
Now, there are some that call themselves Christians that think there's nothing wrong with sex (extramarital or before marrige), or stealing, or lying... Believing that breaking God's law is not sin, is just pure FICTION!
But as for the cowardly, the faithless, the detestable, as for murderers, the sexually immoral, sorcerers, idolaters, and all liars, their portion will be in the lake that burns with fire and sulfur, which is the second death.
Revelation 21:8 (ESV)
As obedient children, do not be conformed to the passions of your former ignorance, but as he who called you is holy, you also be holy in all your conduct, since it is written, "You shall be holy, for I am holy."
1 Peter 1:14-16 (ESV)
Shall we say now: "It just sex"?