Having quoted extensively from Spinoza, and re-posted and referred to my own blog entries from two years ago, in order to make a number of points which I might have dealt with more concisely had I addressed the issues afresh and in my own words, I shall endeavour to abstain from further bouts of such unbridled pomposity.
Except to say only this (just in case I need to spell it out):
The reason why restrictions on freedom of speech are injurious, not only to liberty but also to the welfare of the state, is not because some grand moral principle is thereby transgressed, but primarily because when people are prevented from saying what they think, specifically when their opinions are driven from the public space by threat or violence, they may well (according to their nature) seek some other means of making themselves heard. In so far as their diverse experiences may have taught them that threats and violence will, in the public sphere, prevail over reason and debate, they are apt to consider whether they have been wrong, not in their views but in their methods. Thus might they be led to adopt the tactics of their opposers and thereby seek redress by any and all means necessary.
Such a state of affairs, were it to come to pass, would not only be damaging to the welfare of the state but injurious to the liberties of all.