I personally heard a famous preacher on TV say, “Many times those preaching against sin are struggling with sin themselves,” and implying that is not the message of grace. There could be some truth in that because a failure to judge ourselves can affect what we see in others but his statement is not always true. A statement like that can castigate anyone who then would say anything about sin in a message and can lead others to turn their ears away from them because they categorize them as not preaching grace. What he was really advocating was a “no ouchy words” grace message with no mention of words like sin, repentance, judgment, chastening, reproof …. I think we should preach All Scripture.
True grace (the teachings of grace linked to the truth found in the word of His grace), though, does preach against sin. “For the grace of God that bringeth salvation hath appeared to all men, teaching us that denying ungodliness and worldly lusts we should live soberly, righteously, and godly in this present world,” Titus 2:11, 12. The word of His grace (Acts 20:32) is full of warnings and teachings against sin (Romans 6:1, 15). It doesn’t stop there but it also teaches there is a remedy for what is called sin and His name is Jesus. The same grace that saves also sanctifies or the same grace that takes us out of sin can take sin out of us. True grace teaching is not afraid to mention sin because it gives hope and freedom from all sin: its penalty, power, and one day in the future, its presence.
Could it also be that preaching against sin has come from true godly sorrow that works repentance and has brought forth fruits of repentance “… carefulness, …a clearing of yourselves…vehement desire … zeal … revenge …,” (2 Corinthians 7:10, 1) against a particular sin as well as a love of righteousness and hatred of iniquity (Hebrews 1:9)? Maybe I have a different Bible but in the N.T. the Apostle Paul who had the revelation of grace seemed to follow a pattern in the epistles of talking about the positional truths of grace (what God did for us in Christ) as well as the practical truths of grace against sin (what we are to do because of our actual condition or state of our current walk). We can err by overemphasizing just one side of these truths. Our responsibility is to get our walk, our actual condition, our state, up the level of our position and standing in Christ. When a person sees they are living in sin or their walk is out of line with who God made them to be in Christ, they can change and then walk worthy of the Lord.