"Therefore the Lord will take no pleasure in the young men, nor will he pity the fatherless and the widows, for everyone is ungodly and wicked, every mouth speaks vileness. Yet for all this, his anger is not turned away, his hand is still upraised." NIV translation
David knew of God's love but he also knew that God was a jealous God. This verse speaks to the fact that all of the people have turned away from the things of God and so His wrath is poured out on them. Today, we pretty much ignore the fact that God is going to pour out His wrath on those that turn their back on His offer of grace and mercy (see Revelation 16). But, whether we want to acknowledge it or not, it is coming soon.
"Surely wickedness burns like a fire; it consumes briers and thorns, it sets the forest thickets ablaze, so that it rolls upward in a column of smoke." NIV translation
Briers, thorns, and weeds are usually symbols of sin and disobedience in the Bible. This verse speaks to the fact that all who walk in those ways will be consumed in the fire of God's wrath.
"By the wrath of the Lord Almighty the land will be scorched and the people will be fuel for the fire;" NIV translation
In Genesis chapter six, God poured out His wrath in the form of a flood. This time, it will be in the form of fire as the fourth angel pours out his bowl of wrath (see Revelation 16:8 & 9).
"On the right they will devour, but still be hungry; on the left they will eat, but not be satisfied. Each will feed on the flesh of his own offspring." NIV translation
This verse speaks about a time to come in which things get so bad that the people resort to eating human flesh. At first, we may say that this could never happen but Revelation 13 speaks of a time when people cannot buy food unless they worship the beast. When people get desperate, they do desperate things. For those of us who are in Christ, we will not be here to worry about this but we need to warn those that are not saved that it is coming.
"Manasseh will feed on Ephraim, and Ephraim on Manasseh; together they will turn against Judah. Yet for all this, his anger is not turned away, his hand is still upraised." NIV translation
The judgement on God's people will be so severe that they even turn on their fellow Jews. These events have already happened once but they are also going to happen again in the last days.