John Calvin in his Institutes provides a reminder we should be careful who we “deny the title of church” to.
Among the Corinthians it was not a few that erred, but almost the whole body had become tainted; there was not one species of sin merely, but a multitude, and those not trivial errors, but some of them execrable crimes. There was not only corruption in manners, but also in doctrine.
What course was taken by the holy apostle, in other words, by the organ of the heavenly Spirit, by whose testimony the Church stands and falls? Does he seek separation from them? Does he discard them from the kingdom of Christ? Does he strike them with the thunder of a final anathema? He not only does none of these things, but he acknowledges and heralds them as a Church of Christ, and a society of saints.
If the Church remains among the Corinthians, where envyings, divisions, and contentions rage; where quarrels, lawsuits, and avarice prevail; where a crime, which even the Gentiles would execrate, is openly approved; where the name of Paul, whom they ought to have honored as a father, is petulantly assailed; where some hold the resurrection of the dead in derision, though with it the whole gospel must fall; where the gifts of God are made subservient to ambition, not to charity; where many things are done neither decently nor in order: If there the Church still remains, simply because the ministration of word and sacrament is not rejected, who will presume to deny the title of church to those to whom a tenth part of these crimes cannot be imputed?
How, I ask, would those who act so morosely against present churches have acted to the Galatians, who had done all but abandon the gospel (Galatians 1:6), and yet among them the same apostle found churches?
Calvin, John (2002-12-18). Institutes: Christian Religion (Kindle Locations 18231-18242). Packard Technologies. Kindle Edition. (Paragraphing Mine)