Here is a quote from John Davenant’s commentary on Colossians, which is published by Banner of Truth. He commenting on Paul’s use of “saints” in Colossians 1:2.

Whereas the Apostle calls not this or that good man, but the Colossians promiscuously, saints, as many as put on Christ by baptism; hence we learn that we must think and speak well of all who profess religion, unless by clear and manifest deeds they shew themselves to be ungodly and hypocrites. For the Apostles always, when they descend to particular men and churches, presume every Christian to be elect, sanctified, justified, and in the way of being glorified, until he himself shall proved himself to be wicked or an apostate. So Paul writing to the Corinthians affirms indiscriminately concerning them Ye are washed, ye are sanctified, ye are justified, I Cor. 6:11. For in those things which relate to faith, we must speak and think according to Scripture, which is a certain and infallible rule: so, in other things which relate to charity it is sufficient to think and speak according to the probability of appearances. This rule may deceive; yet not by any fault or hazard of him who thought better of another than he truly deserved, but rather of that hypocrite who was a different and much worse man than he appeared to be.

This rule is solid and the only way to make sense of the way the Apostles’ write while at the same time holding that not all who are in the church are actually saved. I think the 21st century context may need a bit more nuance than this, but it is still good rule to follow. His last point is a good one. If a person assumes that a professing Christian is saved, yet they prove apostate the fault does not lie with the one who showed charity in judgment, but rather with the hypocrite.