I have been meaning to post this from Bonhoeffer for a while – it is most insightful.
Do not give dogs what is holy; and do not throw your pearls before swine, lest they trample them underfoot and turn to attack you (Matt. 7:6). The promise of grace is not to be squandered; it needs to be protected from the godless. There are those who are not worthy of the sanctuary. The proclamation of grace has its limits. Grace may not be proclaimed to anyone who does not recognize or distinguish or desire it. Not only does that pollute the sanctuary itself, not only must those who sin still be guilty against the Most Holy, but in addition, the misuse of the Holy must turn against the community itself. The world upon whom grace is thrust as a bargain will grow tired of it, and it will not only trample upon the Holy, but also will tear apart those who force it on them. For its own sake, for the sake of the sinner, and for the sake of the community, the Holy is to be protected from cheap surrender. The Gospel is protected by the preaching of repentance which calls sin sin and declares the sinner guilty. The key to loose is protected by the key to bind. The preaching of grace can only be protected by the preaching of repentance.
Not sure I can add much to that, other than to observe that the preaching of repentance does not seem to be a popular thing these days. Which is why it is very likely to be all the more needed.