Free Speech (or not)

I was reading about the US pastor who has organised a book burning of the Koran on September the 11th, "It is possibly time for us in a new way to actually stand up, confront terrorism". I really don't know whether his event could actually have any genuine benefit other than stirring up hatred but it certainly does raise interesting questions about free speech. Of course, it is not just his speech which will cause trouble but the excessive use of that 'freedom' to go into the realms of provocation but is this wrong?
What exactly is free-speech? In a sense we do not have free speech in the UK. I can be charged with "inciting racial hatred" and presumably various homophobic speech crimes which can be a very broad brush against my supposed "right" to express my own opinion.
The origins of the idea of free speech come from various political and religious attempts to silence dissenters under the legal system which would then prevent the intended operation of democracy where the voice of the population could be silenced by a miniority only because they happened to be in government.
I guess the question is, where does this freedom end and responsibility begin? It is all very well saying, "I think Islam is a terrorist religion" and leaving it at that but I guess this guy thinks unless he ups the ante, he won't get enough people to agree with him to do something about it (whatever that might be).
Look at Nelson Mandela. Back in the day he was accused of terrorism and inciting violence and hatred but his cause has only been redeemed over time and he presumably argued that he had no choice to change the system in any other way. I guess pastor Terry Jones thinks the same thing.
Will time show him to be correct or will he simply get silenced by those who preach tolerance and freedom as the tenets of civilisation on the one hand and yet avoiding conflict with anyone who might not agree!?
I guess I have that niggling conflict, "why does the pastor have to tolerate Islam but Muslims do not have to tolerate him"?