If this is the exception rather than the rule, then we shouldn't sacrifice any rights.
However, if islamISTS or communISTS or nazISTS or anyone else decides to take advantage of a liberal society and attempt to overthrow it, systematically, shouldn't there be some way to prevent it?
I don't know what's worse, McCarthyism or allowing unlimited growth of violent revolutionary ideas. Of course, the civil libertarian in me says that freedom of expression should be maximized. But I also realize that there are mind viruses out there that compete with liberalISM and despise it for one reason or another. The question is, how intolerant should we be of intolerance? In the United States, for instance, we have become very intolerant of racists and homophobes.
I am not talking about this particular incident.