False doctrine inoculates people against the truth.

It’s certainly not a complete or unbreakable inoculation, but it makes it more confusing and harder for the truth to set in. Here in the U.S., there’s a church on every street corner, but many are not preaching the true Gospel. They are creating confusion and actually inoculating people against the truth because people think they understand what Christianity is, when in reality, they’ve been practicing something completely different. So they may get burnt out or declare that it “doesn’t work”, because they’ve been doing the wrong thing. And then when you try to tell them the truth about Christianity, they don’t want to hear it, because they think they already understand it and it has let them down. This is like what Jesus was saying in Matthew 23:15 - “Woe to you, scribes and Pharisees, hypocrites! For you travel land and sea to win one proselyte, and when he is won, you make him twice as much a son of hell as yourselves.”