We all have ways of justifying our actions, even when we know deep in our hearts they are neither biblical nor good for us. We can rationalize almost any behavior, as if we're looking for loopholes and exceptions to God's clear commands.
I have a friend (who is not a close friend, but a friend nevertheless) who claims to be a believer in Jesus Christ. Let's call him Carl. In recent years Carl has married a woman whom he knew to be trouble, with a capital T, from the get-go. She and he even had pre-marital counseling in a Christian context. In spite of godly counsel, they committed fornication and she became pregnant. They married, and within a year, they divorced. She went back to drug addiction and Carl was forced to care for the son who was born to them.
Fast forward ten years, and Carl has had a succession of girlfriends, with whom he has committed fornication. In conversations with Carl, I've pointed him to scriptures that prohibit sexual sins, and since these girlfriends are not Christians, I've also warned him about being unequally yoked together with unbelievers. His unbiblical behavior continues.
Carl's latest rationalization is what I call the "missionary relationship" with an unbeliever. In short, Carl believes that his relationship with a woman whom he knows is not a Christian is an opportunity to influence her for Christ. Moreover, in his opinion, she keeps him in line, so to speak, and holds him accountable to a higher standard, knowing he claims to be a Christian.
Is Carl being a missionary in this situation? Of course not! If he is truly a Christian (and I have some doubts about this), will not God hold him responsible for his clear disobedience? Of course He will.
Again, I find it amazing how we all can rationalize our disobedience to God. God, however, sees through our excuse-making, and He wants us to obey Him, but He will not force us. Rather, God wants us to do the right thing, for three reasons: 1) because God says not to, and God knows best; 2) because we love God and want to please Him, even when we find it difficult to do so; and 3) because the world is watching us, and God wants us to be light in a dark world, which is impossible to do when there is willful darkness in our lives.