By the cross God displayed two things with absolute clarity ---
A) God hates sin. He hates sin so much that His own son took upon himself all the sins of those who would come to believe in him... and bore full punishment for those sins. The death that Christ died, the bloody, painful, brutal death that Christ died.... was a clear picture of how greatly our Holy God despises sin.
B) God loves men. He loves them so much that through the cross he effected a means of their forgiveness. He loves them so much that He willingly took upon himself their sins and the punishment for those sins. God loves mankind.
But here's my point: You cannot simply preach "God is Love" without first showing the depths for which a Holy God despises the sinfulness of men. These two things are bound up together and are the necessary starting points of repentance and salvation --- a man cannot be saved until he sees himself a sinner, and in Christ's crucifixion sees the just punishment of his own sins. It is not merely enough that a man believe "God is love" and then live his life however he so desires.... he must likewise understand the gravity of his sin.