I've severely re-edited my post for brevity, clarity and understanding. I've added my content inside numbered parenthesis (1. Black-Bloc/Anarchists), (2. violence, destruction), (3. G8-G20 fortress and police state.) in the quoted paragraph below.

As Marshal McLuhan said, "The Medium is the Message". I think the federal government and the police understood the "message" of violence and destruction the "medium" (Black-Bloc/Anarchists) transmits and acted in accordance with McLuhan, "Anticipation gives the power to deflect and control force."

"Why is this understanding of "the medium is the message" particularly useful? We tend to notice changes - even slight changes (that unfortunately we often tend to discount in significance.) "The medium is the message" tells us that noticing change in our societal or cultural ground conditions indicates the presence of a new message, that is, the effects of a new medium (1. Black-Bloc/Anarchists). With this early warning, we can set out to characterize and identify the new medium before it becomes obvious to everyone - a process that often takes years or even decades. And if we discover that the new medium brings along effects that might be detrimental to our society or culture (2. violence, destruction), we have the opportunity to influence the development and evolution of the new innovation before the effects becomes pervasive. As McLuhan reminds us, "Control over change would seem to consist in moving not with it but ahead of it (3. G8-G20 fortress and police state). Anticipation gives the power to deflect and control force. (McLuhan 199)"
http://individual.utoronto.ca/markfederman/article_mediumisthemessage.htm