Verse 6 is nearly a repetition of Jeremiah 7:32. Jeremiah has been sent to proclaim the word of God in the valley of Hinnom to those who are guilty of the very worst of sins: the offering up of their own children.
We see again that when God punishes, he frequently designs a punishment which matches the sin committed. Of course, the Lord is able to calculate according to his perfect justice, what would be the right punishment to meet the crime in some totally separate domain. So in human justice, a man is fined for committing a traffic offence, and human justice attempts to set a suitable fine. But often God designs a punishment in the same domain. So here, the people have exceeded all wickedness by offering up their own offspring, and God brings them into such straits that they are willing to degrade themselves in such a fashion. This too is justice. It is a form of justice which draws attention to the awful nature of the crime, by matching it in its degrading horror.
Who would want to make an enemy of the all-powerful God on high? Who can defend themselves when he begins to fight against them? We cannot stave off his judgments, or avoid what he has in store for us. He is able to outthink us, to outmanoeuvre us, to trap us so that no amount of human ingenuity or forethought can protect us.