Found over on MercyJourney:
The Missouri Synod Lutheran cannot understand that a properly called but heterodox pastor, Lutheran in name only, is permitted to lead a whole congregation, a whole generation of the flock that has been entrusted to him, into misbelief and even unbelief, while the ecclesiastical authorities keep silence and even maintain that the congregation is still Lutheran, because the Lutheran doctrine alone has standing, is publica doctrina, there. Is he incorrect? Who has the right to forbid the Gospel to be preached to these cheated souls by someone else? But how is it if there is not a clear case of false doctrine, but a mere suspicion? What clear facts must be evident before it is permissible to establish pulpit against pulpit, altar against altar? Is it not understandable that in questions of this kind there have been frequent differences of opinion, misunderstandings, and severe conflicts? What appeared to the one side as Christian missionary duty, the other side saw as proselytizing, that perversion of true mission work, against which Christ Himself warned the church when He held before her in Matt. 23:15 the frightful example of the mission work of the scribes and the Pharisees. Missouri would be no Lutheran Church if she had not asked herself again and again on what her understanding of the missionary duty of the church is founded. Missouri would have no right to call herself Lutheran had she not again and again measured her own actions by the Word of God, and acknowledged and confessed her own sins. However, the errors and sins which were committed in this area do not change the fact that this church has recognized the missionary duty of Lutheranism. The Lutheran Church does not exist merely to preserve the religious home of those people who by historical chance and by the manner in which they were led bear the confessional stamp “Lutheran.” Rather, it is her task to preach to all men she can reach the Gospel as it was rediscovered during the Reformation and attested to in the Lutheran Confessions. This is being done today in a particularly effective and impressive way in the all but worldwide radio mission of The Lutheran Hour.
Sasse, Letter 20 (soon to appears in Letters to Lutheran Pastors II)