In lamentations, God punishes Jerusalem with such a ruthless force that anyone could easily look on him as an enemy to the city. It is difficult to see it otherwise. He brings enemies to the city, drives mothers to cannibalism and slaughters an entire city. It is easy to ask, "How could this God love these people? How could he want the best for them?" And yet this story isn't just about Gods power and his vengeance, it is also an example of his love. He was "like an enemy" but not one, because he had the good of their souls at heart.
At its core, this is a story about hope. Hope that whatever happens, so matter how terrible, how far you seem to have fallen from grace, that god has a higher plan and the good of you soul in mind. That he will give you another chance. "the lord is good to those who wait for him...it is good for one to bear the yoke in silence when the lord has imposed it...for the lord will not reject forever. Although he causes grief, he will have compassion according to the abundance of his steadfast love; for he does not willingly afflict or grieve anyone. (Lamentations "3:25-3:33)
In the early days of Christianity, the extremes found in Gods biblical punishments were not uncommon in the real world. Famine, war, murder- they were all real occurrences and people needed explanations and reassurance that it wouldn't happen to them, or that it would end. No doubt the Lamentations is an explanation of the fall of a real city; all stories have their basis in fact. The comfort of the story is that is was Jerusalem's fault, for they had sinned. And their punishment would end when God felt it was the right time.