Sometimes we want to pull back from saying as much as God says about a particular sin, or about Christ being the only way of salvation. That would be a grave mistake, because if we really do have the truth, whom do we serve if we do not faithfully share it? Nobody but the devil. The gospel inevitably arouses opposition from sinful men, but we shouldn’t let that stop us. If we continue in what we have learned, we will be saved. Martin Luther comments:
When Christ foresaw in the spirit that a great disturbance and revolution in the world would follow His preaching, He comforted Himself this way (Luke 12:49): “I came to cast fire upon the earth; and would that it were already kindled!” Thus we see today that because of the persecution and blasphemy of our opponents and the contempt and ingratitude of the world many evils follow upon the preaching of the Gospel. This bothers us so much that we often think, according to the flesh, that it would have been better if the teaching of godliness had never been circulated and peace had been preserved than that the public peace should be disturbed as it has been since it was made public. But according to the Spirit, we courageously declare with Christ: “I came to cast fire upon the earth; and would that it were already kindled!” Once this fire has been kindled, great upheavals immediately arise. For it is not some king or emperor but the god of this world (2 Cor. 4:4) who is provoked; and he is a powerful spirit and the lord of the whole world. This great adversary is attacked by the weak Word that preaches Christ crucified. Feeling its divine power, Behemoth stirs up all his limbs, shakes his tail, and “makes the deep boil like a pot” (Job 41:31). This is the source of the tumult and uproar in the world.
Therefore we are not impressed when our opponents are offended and shout that no good will come of the preaching of the Gospel. They are blind, faithless, and stubborn; therefore it is impossible for them to see any of the benefits and results of the Gospel. On the other hand, we who believe see the enormous and innumerable benefits and results of the Gospel, even though outwardly and temporarily we are oppressed by many evils, despised, despoiled, slandered, condemned, the περίψημα of all things (1 Cor. 4:4), put to death, and inwardly crushed by the consciousness of our sin and vexed by demons. For we are alive in Christ, in whom and through whom we are kings and lords over sin, death, the flesh, the world, hell, and every evil; through Him we tread underfoot that dragon and basilisk who is the king of sin and death. How? In faith. For our blessing has not yet been revealed. But meanwhile we await it in patience and yet already possess it certainly through faith. (emphasis mine)
Luther, M. (1999, c1963). Vol. 26: Luther’s works, vol. 26 : Lectures on Galatians, 1535, Chapters 1-4 (J. J. Pelikan, H. C. Oswald & H. T. Lehmann, Ed.). Luther’s Works (26:vii-453). Saint Louis: Concordia Publishing House.