I suppose it has always been easier for Christians and especially preachers to concentrate on the love, mercy and grace of God than to think about the fact that God also hates and has holy wrath toward both the sinner and his sin. Pretty soon we begin to come up with formulas to separate God into compartments to take some of the edge off his holy wrath. We have all heard the saying, "God hates sin but loves the sinner". At first glance that seems to take the edge off of things but it is just an unfortunate, rather misleading statement. There is an element of truth in it but it is far from accurately conveying God's attitude toward sinners.
In the first place you can't separate sin from the sinner. Sin is in its essence an act of rebellion. All sin is shaking your fist before God with the idea that you will do what you want to do. To say that God hates your hatred of him but loves you anyway just doesn't paint the full picture. Whether we like it or not the Bible says, Psa 5:5-6 "The boastful shall not stand before your eyes; you hate all evildoers. You destroy those who speak lies; the LORD abhors the bloodthirsty and deceitful man." This isn't to say that the Lord doesn't love and hate at the same time but our problem is that we don't have a problem being loved but we just don't like being hated, especially by God. The reason God hates sin is because a just God must be against people not worshipping him alone and he is right and just to do so.
Perhaps one reason some think they can separate themselves from their sin is because we sometimes make sin a substance in us, not a deliberate act or thought we do and have. We say whiskey or cigarettes are sinful; this is a sin or that is a sin as if sin is separate from our wills. But sin isn't found in a bottle and it is far more than just an act we perform. When we make sin merely something separate from ourselves it is easy to stand with God against it and begin to think pretty highly of ourselves. But there is no sin unless our sinful wills are involved.
But there is another problem we have today that is even worse than distorting God's wrath and that is to deny it altogether. There are plenty today that are telling us that God doesn't hate anyone; he is just a God of love and the only sin we have is that we won't accept his love for us (read Robert Schuller, Rob Bell, etc.) Those that only believe that God is gracious and merciful but deny that he is one who hates sin and will judge sinners take away the basis for grace.
One only is gracious and merciful to those who are deserving of judgment; those that have offended the law and stand condemned. Without the guilt of sin and the judgment of a holy God there is absolutely no need of grace and mercy. In fact, if we are all just innocent victims of God's providence then he actually owes us grace.
To think that God has no right to judge rebels turns everything the Bible teaches upside down. Take away the wrath of God towards sinners and the cross of Christ makes no sense. Why should God's Son suffer the wrath of the Father if none of us were in any danger of facing his wrath and needed to have it averted somehow? Take away God's wrath toward sinners and you take away any need of proclaiming the gospel. The gospel is good news because it reveals a way to escape God's wrath. If there is no wrath there is no need for escape. The grace and mercy of God is that he provided a way to be saved from his just wrath. To deny Hell removes any need for grace. And if the Bible teaches anything it is that without grace none of us have any hope. Therefore all of us come into this world under God's just wrath.