What is Abu Hanifa's evidence for the impermissibility of the congregant reciting Al-Fatiha in a loud or silent prayer?

The Hanafi school of thought holds that the congregant (ma'mum) should not recite behind the Imam in either silent or audible prayers, but rather should listen attentively and remain silent. They base this on the Almighty's saying: "And when the Qur'an is recited, then listen to it and pay attention," and on the Prophet's (peace be upon him) saying: "Whoever has an Imam, then the Imam's recitation is a recitation for him." They interpret the hadith: "Then recite what is easy for you from the Qur'an" as referring to situations other than praying behind an Imam.