The medium which transmits a message has its own powerful social effects, irregardless of the message transmitted. The most fundamental difference is oral v.s. Speech is natural, keeps senses balanced and harmonious, makes people closer to each other and closer to nature.
Writing is artificial, detached, and encourages lying, social fragmentation, and alienation.
Both analog and digital representations are equally capable of transmitting the same information. IT revolutions occur in tandem with dramatic social changes, so it may appear to be the cause when it is not. Rousseau and McLuhan are just repeating the Christian story of the fall from the garden of eden.