What is the response to the claim that the books of the Imams of the Salaf have been distorted?

Question:
If someone says that the books currently in our hands from the books of the Imams, such as the books of Imam Ahmad ibn Hanbal and Shaykh al-Islam Ibn Taymiyyah, are distorted, and asks how these books could have reached us through these long centuries free from distortion, while he denies the existence of the Imams in the first place and asks how it is established that there was a man named Ahmad ibn Hanbal, for example, what is the response to this? And what is the advice?

Answer:
The response to him is that these matters have been transmitted by mass transmission (mutawatir) and are known to the scholars. They knew who wrote them and who said them, through the transmission of scribe to scribe, or scholar to scholar, via authenticated and known manuscripts and authenticated signatures. Whoever denies this is a disbeliever. This is a denial of reality, a denial of a known reality, and a lie. It means lying to the Imams and scholars, and denying something upon which people have reached consensus and which people know. After this, he says, "There is no Muhammad and no Companions!" The end of it. Those who transmitted these books to us are the same ones who transmitted the reports of the Companions and the reports of the Prophet (peace and blessings be upon him). So whoever denies the existence of the Prophet and the existence of the Companions, and denies the existence of the scholars, his intellect and his religion are destroyed and gone. We ask Allah for safety.