Lamentations 4-5

It took less than 10 minutes to read this passage. In 4:6 Jeremiah sums up the transgression that led this total destruction of Judah; the sin of the people. Yet Jeremiah says that the sin of Judah was greater than the sin of Sodom. From our vantage point we might find such a statement difficult to substantiate, but that is the reason God gives his prophet. So the question is: why did God describe Judah's sin with those words?
Stuart