> Correct, but for that argument to hold within the 
   > context of this case we would need the government to 
   > show that most people who visited this site did so with 
   > the intent to incite imminent lawless action. 

Of course that's not true. For the government to prosecute all of those visitors requires additional proof, to be sure. However, for the government to gather evidence on a subset of those visitors who have already been arrested and are being charged with politically inspired violence, is perfectly appropriate.