What is the ruling on praying behind an Imam who criticizes scholars such as Yusuf al-Qaradawi, Ibn Baz, Muhammad ibn Salih al-Uthaymeen, and Ibn Taymiyyah?

Prayer behind an Imam who backbites scholars is valid, but he must be advised and informed of the impermissibility of slandering scholars and the obligation to revere them and recognize their rights. Indeed, scholars are not infallible, and their errors do not justify disrespecting them.