Rightly dividing the Word
2 Timothy 2:15 NKJV
Be diligent to present yourself approved to God, a worker who does not need to be ashamed, rightly dividing the word of truth.
To understand the Bible better you need to look at the audience. In the Epistles Paul is instructing people IN THE CHURCH, not judging those outside our fellowship, but regarding those who claim Christ but do not follow Christ.
1 Corinthians 5:9-11 (BBE)
In my letter I said to you that you were not to keep company with those who go after the desires of the flesh; But I had not in mind the sinners who are outside the church, or those who have a desire for and take the property of others, or those who give worship to images; for it is not possible to keep away from such people without going out of the world completely: But the sense of my letter was that if a brother had the name of being one who went after the desires of the flesh, or had the desire for other people’s property, or was in the way of using violent language, or being the worse for drink, or took by force what was not his, you might not keep company with such a one, or take food with him.
Paul says do not keep company with people who say they are Christians but they don’t act like Christians