Does the obligation to listen to the khutbah cease if the Imam condemns what ought not to be condemned, or praises what ought not to be praised?

One must listen attentively to the sermon, based on the Hadith: "If you say to your companion on Friday to 'listen attentively' while the Imam is delivering the sermon, you have engaged in idle talk." This is unless the preacher engages in idle talk during his sermon and speaks about matters of no benefit; then, it is not obligatory to listen attentively. Ibn al-Musayyab did indeed do this.