The question comes up every time a Christian makes music that does not sound like a worship set. Can you cuss? Should you? Does it mean you are not really saved? The short answer from the text is that belonging to Christ is not the same thing as a perfect record of words. I am a sinner. I am not going to pretend otherwise. Once saved always saved. Not sorry about it.
Paul describes the ongoing struggle that remains inside the believer (Romans 7) and then declares there is no condemnation for those who are in Christ Jesus (Romans 8:1). The standard is real. It is not a demand for sinless speech as the condition of remaining saved. 1 John sets a high ideal and then says that if anyone does sin, we have an advocate with the Father, Jesus Christ the righteous (1 John 2:1–2). The people Jesus says he never knew in Matthew 7 are appealing to works. He does not say they once belonged and then lost it. Genuine believers already belong to him.
That does not make crude language the goal. It means the presence of it does not reclassify a person who has believed and confessed as never known. James rebukes barren profession inside the community without making works the ground of salvation. The warning calls believers to get the heart right and prioritize the main thing. It does not create a path from belonging to being cut off. Fruit and cleaner speech are the right way to live and the proper response to grace. They are not the condition that places a person in Christ or keeps them there.
I write and record as a Christian who still sins. The music is not an attempt to perform cleanliness for an audience. It is the work of someone who has been secured and is still walking through the valley. Readers can examine the passages. They can disagree. The claim here is narrow: a Christian artist does not have to pretend he is not a sinner in order to be one.