The debate in the beginning of Acts 15 is virtually identical to the heresy in Galatians where Paul is combating the idea of making circumcision part of justification (being declared righteous by God through faith alone in Christ). What’s most insightful in that epistle is that Paul informs his readers of the motive behind this false teaching—avoiding persecution. He hints at what happens when the pure gospel is preached in 5:11 But if I, brothers, still preach circumcision, why am I still being persecuted? In that case the offense of the cross has been removed. This brings such great clarity into false teaching in that it always seeks to remove the offense of the cross. Paul makes this explicit in Gal. 6:12 It is those who want to make a good showing in the flesh who would force you to be circumcised, and only in order that they may not be persecuted for the cross of Christ. You can always know that when someone adopts false teaching, there is a certainty that they are seeking to protect themselves from something. This means that there’s something about the biblical teaching of the cross that is too costly for them to bear.
This is why it is essential for all of us to do as Paul told Timothy in 1 Tim. 4:16…pay close attention to your life and your doctrine. If we don’t do both of those things, the pressures of being a faithful Christian will wear us down and eventually we will turn away from the truth. Sadly, and even in the time of Galatians, this doesn’t mean you have to abandon some sort of profession of Christ since there are many Christs out there and many gospels. Only fighting hard to guard the clarity of the gospel, will keep us from being deceived by all the false teaching out there. This is what we see in Acts 15 as the gospel is protected through great debate and discussion.