The obvious thing here is that Christians aren't called to cease interacting with "sinners", or avoid business with "sinners". As St. Paul writes,
"I wrote to you in my letter not to associate with sexually immoral persons— not at all meaning the immoral of this world, or the greedy and robbers, or idolaters, since you would then need to go out of the world. But now I am writing to you not to associate with anyone who bears the name of brother or sister who is sexually immoral or greedy, or is an idolater, reviler, drunkard, or robber. Do not even eat with such a one. For what have I to do with judging those outside? Is it not those who are inside that you are to judge? God will judge those outside." - 1 Corinthians 5:9-13
The Apostle here refers to his previous letter to the Corinthians (which we don't have and is lost to us), and how he told them to not associate with certain people, but he makes it clear that he's not talking about people outside of the Church, but specifically means people in the Church. People who call themselves Christians but engage in certain toxic behaviors and show no remorse for their behavior. The statement "do not even eat with such a one" comes across as harsh, but is best remembered to be in a context of a period where sharing a meal in one's house with someone was an act of intimacy, and here a Christian who so flagrantly acts in such a toxic manner should not have their toxic behavior validated by intimate fellowship. Fundamentally here, Paul says that he--nor we for that matter--are in any position to judge those outside of the Church, because that's not our business here. We can't force our own ways upon those who aren't committed to the same things we are: e.g. a Pagan offering a sacrifice to their gods at the local temple is a very different thing than if a Christian, who confesses there to be only one God and the worship of false gods to be idolatry, to do the same thing. As Paul says here, if we were not to associate with those outside of the Church at all, then we'd have to somehow leave the world, such a thing is both impossible and superfluous.
Paul is concerned with the integrity of the community, that those who call themselves Christian ought not engage in certain behaviors which are toxic and completely forbidden in the Church--idolatry, alcohol abuse, extortion, abuse, or prostitution (translated as "sexually immoral" here). It's worth noting that some of these terms don't carry the same intensity and severity in their English translation as they do in their Greek, translated as "reviler" here refers to an extremely abusive person, someone who is excessively cruel with their words and seeks to demean, threaten, and hurt another person with language; and translated as "robber", sometimes as "extortioner", speaks not merely of someone who steals, but rather a "rapacious person", someone who violently takes by force.
Frankly, a Christian who uses deceit, manipulation, and such measures to avoid engaging honestly, kindly, respectfully, and lovingly with other persons is probably the exact sort of person that Paul would suggest is engaging in a sort of toxic behavior that brings disrepute to the Church.
-CryptoLutheran