I think that the present generation has lost the capacity to mourn rightfully. To mourn means to grieve over a death. To mourn implies that something has died. For those who seek the Kingdom of God and long for righteousness, the death of truth and justice on the streets elicits intense grief and mourning. The mourners are the ones who stand in the gap; they are the intercessors; and, where there is the absence of true mourners, judgment is imminent (Isaiah 59:14-16).
In his letter to the Corinthians, Paul rebukes the Church for being puffed up rather than mourning over sin in the camp (1Cor.5:1). Grace is not an excuse for licentiousness (Jude 1:4). The truth is that Grace teaches us to say "no" to worldly lusts and to live godly and righteous lives in this world (Tit.2:12). Grace doesn't teach us to overlook, ignore, or tolerate sin. It teaches us to love sinners; but, that love breaks our heart with grief over the state of sinners, because sin means death. When values die, it is not just the case that values die; people die as well. Therefore, the mourning is two-fold: over the loss of justice in the world and over the fall of the people away from God.
A powerful picture is painted for us in the book of Ezekiel chapter 9.
Then He called out in my hearing with a loud voice, saying, "Let those who have charge over the city draw near, each with a deadly weapon in his hand." And suddenly six men came from the direction of the upper gate, which faces north, each with his battle-ax in his hand. One man among them was clothed with linen and had a writer's inkhorn at his side. They went in and stood beside the bronze altar. Now the glory of the God of Israel had gone up from the cherub, where it had been, to the threshold of the temple. And He called to the man clothed with linen, who had the writer's inkhorn at his side; and the LORD said to him, "Go through the midst of the city, through the midst of Jerusalem, and put a mark on the foreheads of the men who sigh and cry over all the abominations that are done within it." To the others He said in my hearing, "Go after him through the city and kill; do not let your eye spare, nor have any pity. "Utterly slay old and young men, maidens and little children and women; but do not come near anyone on whom is the mark; and begin at My sanctuary." So they began with the elders who were before the temple. (Eze 9:1-6 NKJ)One must not forget that if God expects anyone to mourn, it is the people of the sanctuary, the people of God. But, when God's people lose their capacity to mourn over sin, when salt loses its saltiness, then hope is distant, and judgment begins at the house of God (1Pet.4:17).
To mourn implies to weep bitterly because of the evil that sin brings on those who reject God. Jesus wept over Jerusalem when He drew close to it and saw it (Luke 19:41) because He knew what evil its rebelliousness was going to bring upon it. There was a reason why Jesus was so violent against sin in the Temple and why His words were so red-scorching against the Pharisees. The reason was because Jesus was full of Grace and Truth and He loved people truly and came to save them. Any modern preacher of grace who is so caught up with grace that he loses sensitivity to grieve and mourn over sin, doesn't know the true Grace of Christ. The true Grace of Christ knows the price of sin; it is a weeping grace; it is also a violent grace that will snatch the sinner from the flames of fire (Jude 1:23). Those who truly know God cannot but mourn over sin; and blessed are those who mourn, for they shall be comforted.