Jeremiah - the law and evangelism

At Think15 today, the pastor spoke from Jeremiah chapters 1-2. I found two points very interesting:

1. Jeremiah describes Israel's relationship between  God and them as a bridegroom and his bride.  Jeremiah then tells about how Israel wandered and chose to worship idols. The speaker pointed out that because of that relationship, worshipping idols was tantemant to adultery! Ouch!
2. Martin Luther,  when asked how he evangelized, said he spoke of Grace a little (Jer 1), spoke of the law (Jer 2),  so they would know they were sinners, spoke of the law more so they could feel the guilt,  spoke of the law yet again,  then ended with a full blown recitation of God's mercy...because until they understood thoroughly that they were sinners they didn't understand they needed Christ.