When there is no peace. The false prophets will proclaim peace when there is no peace because that is a message which will be believed by many. It is a favorable message. We would wish for the best. We would desire that the Lord would go easy on us.
Peace is the message the people want to hear.
In fact, you could say our ears itch to hear the message of peace. Second Timothy mentions how the motivation to hear certain things can lead us to listen to false prophets. In our text, Jeremiah responds to this false prophecy from Hananiah. In other words, he would like it to be true. He would like the mistreatment of Judah to end soon.