I have heard this passage used to justify that we can and should remain in our sins; specifically in cultures that are sinful and have counter biblical ways of living. But the call here, to stay in a circumstance is toward domination of the environment rather than abandonment. There is never to be a mentality of leaving but rather one of allowing a radical internal change to permeate a toxic environment till it no longer is toxic. The caveat is that if your circumstance releases you then you can leave… as in the example of a freed slave. However, Paul in this example, highlights that a free man lives enslaved to Christ in mentality. And this is the crux. Don’t change the environment. Change the people and reform of the environment is natural. This is why, wherever the gospel has been received seriously, social services and reform have taken place in every culture. Whether it was husbands loving wives in Rome, or orphanages in Europe.