Love warns and that is true. People today tend to say, "Stop preaching against other people's religions, didn't the Bible tell us to love one another." What they don't realize is that the "love gospel" is not love at all. If you love people, you would tell them that they are heading for Hell, you would not sugarcoat the Gospel just because you are afraid that the lost sinner would be upset. Jesus loves sinners so much He told them the plain truth that they are heading for Hell, He never softened the message and to say that any preacher who preaches the full message of the Gospel is not Christlike is a huge lie to the face of any true Christians.
John the Baptist preached against sin and was not afraid to declare the truth even at the cost of his head. When he attacked the incest and adultery of Herod Antipas and Herodias, he knew what he had to do. When he attacked the Pharisees because of their hypocrisy, he was making way for the one greater than him namely the Lord Jesus Christ. He did not pull any punches when it came to false preachers and neither did Jesus. What he did was very Christlike when he genuinely warned people of their need to repent.