People who think they can get away with doing evil in Christ are only deluding themselves. There is no excuse for sin. I mean honestly, who are you kidding? When you turn on the news and or watch a movie, how do you know the good guys from the bad guys? Is it by the fact that they have a belief alone or is by what they do?
In other words, if you don't confess and turn from your sin or evil in your life you are still the villain of the story and you are not the hero or the good guy. If you believe otherwise, then stop rooting for the good guys when you watch a movie. When you happen to come across the news and see people in the world doing horrible acts of evil, you have to say to yourself that they might just be one God's people who also has a belief on Jesus, too.
But we both know that is not the case. Jesus said He would rather a person be cold or hot; and not lukewarm. For Jesus will spew those out of his mouth who are lukewarm. In other words, if someone wants to do evil, leave God out of it because He will not tolerate anyone in getting away with sin or evil.
Choose this day in whom ye will serve.
For believers who sin and don't repent will not be in heaven or the eternal new earth. For Scripture says have no fellowship with the unfruitful works of darkness, but rather reprove them. Scripture also says there are those who have turned the grace of our God into lasciviousness or a license for immorality. Peter talks about how there are false prophets who have eyes full of adultery and who cannot cease from sin. Paul tells Timothy that,
"This know also, that in the last days perilous times shall come. For men shall be lovers of their own selves, covetous, boasters, proud, blasphemers, disobedient to parents, unthankful, unholy, Without natural affection, trucebreakers, false accusers, incontinent, fierce, despisers of those that are good, Traitors, heady, highminded, lovers of pleasures more than lovers of God; Having a form of godliness, but denying the power thereof: from such turn away."
For if anyone teaches they can sin and still (because they have a belief alone on Jesus to be saved) does not understand the Bible or the gospel, and nor do they know God because God is love and God is good. For the Scriptures say he that does not love does not know God; And Paul says that if anyone teaches contrary to the words of Jesus and the doctrine of Godliness is proud and knows nothing.
Side Note:
Oh, and pease take note that I don't believe in Works Salvationism, either. We are saved right here and right now by God's grace (When we repent of our sins and accept Jesus). For it is a free gift. However, like all gifts, one can choose to be irresponsible with their gifts and cause them to be ruined, though.