In 1 Corinthians 5, Paul tackles the church tolerating sin within it. Paul tells the church at Corinth that they are tolerating something that even the Gentiles do not tolerate. Paul advises the Corinthians that this toleration of sin is like tolerating yeast in the dough for unleavened bread. If you do not address and remove it now, it will grow.
We can see this same tolerance in the current Church in America when it comes to several issues and we need to deal with it now before it grows and causes too many problems. Once it grows, it eventually becomes so large that we struggle to see how to deal with it, though we could have cut if off much earlier.