There are so many scriptures that show Christ, the prophets and apostles preaching the message of repentance from sin, that one would have to either willfully ignore them as they read the Bible, or be sincerely ignorant of those scriptures. I have already mentioned quite a few scriptures relevant to that point.
John the Baptist got himself beheaded for condemning Herod's adulterous affair. Paul reasoned with the governor Felix (who was also involved in an adulterous affair) about righteousness, self control, and the coming judgment, and scripture says Felix trembled at Paul's message -Acts 24:25.
Both the OT and NT are filled with such bold preaching on repentance from sin, both internal and external sin.
Ezekiel exhorts us to warn the wicked of their impending death due to their sins against God, lest their blood be required of us:
"When I say to the wicked, 'You shall surely die,' and you give him no warning, nor speak to warn the wicked from his wicked way, to save his life, that same wicked man shall die in his iniquity; but his blood I will require at your hand. 19 Yet, if you warn the wicked, and he does not turn from his wickedness, nor from his wicked way, he shall die in his iniquity; but you have delivered your soul."-Ezekiel 3:18-20
In his first sermon after Pentecost Peter warned the Jews and declared to them that they were guilty of crucifying and murdering the Lord of glory, and what happened? Scripture says they were cut to the heart when they heard that, and they feared and said "Brethren, what shall we do?" And 3,000 souls were saved in one day.
As I studied that sermon carefully I noticed there's not even one mention of the love of God in it. Why? Because Peter knew they needed to understand the seriousness of what they had just done to the Lord of glory. The Holy Spirit used Peter as His mouth piece to convict of sin, righteousness and judgment.
We cannot water down the message and make it palatable to a world that loves sin and hates God. We cannot become part of the seeker sensitive, seeker friendly, and social gospel movements. Those kinds of movements only speak of love and doing social acts of kindness without warning of the need for repentance and faith in Christ.
I can go on and on with example after example of the biblical precedence for preaching against sin in our gospel message to the lost. But I trust that what I have posted so far is sufficient to make the point.