Church discipline visibly demonstrates the seriousness of sin as well as both the holiness and love Christ calls His church to live (Matthew 18:15-20). When church discipline is first implemented, the immediate fallout may appear to be all negative.
However, in time the church will benefit by having honored God with obedience, and the credibility of the church and her message will experience a renaissance. The fellowship in the church body will be more reflective of our Lord Jesus Christ in both love and holiness.
This is not to say that everyone will then believe our message, but whether they believe it or not, they will be evidentially convinced that we do. That is the kind of assurance that is often lacking today.