Quote Originally Posted by Alexander the Pretty Good View Post
Your scenario is as follows:

1. Cleric preaches death on someone
2. Impressionable fools hear it, plan murder
3. Murder carried out

How will arresting the cleric after 1 affect 2 & 3? Until we can read minds (cue techie link from Lemur?) we can't prevent murder by snuffing out "troublemakers" before they commit a crime.
Well, that one would go under hardly preventable, so what about me calling the local radio show and saying I want to mrder the president of the USA and that I'm really serious about it. Would noone care? Freedom of speech or would they at least arrest me and search my home? Also should they do that or shouldn't they?

Also while the impressionable fools plan the murder in your example you can do two things:
1) you can arrest the preacher, doesn't have to be long, for calling for murder, that will show him it's not okay and prevent him from calling for more murders before the first one has been carried out.
It may also give you some time to investigate his organization without him doing any further harm.
If the suspect gets killed he is guilty anyway, isn't he?

2) you can give a bodyguard or two to the person he wants murdered, at least for a certain amount of time, cannot protect them for life but you can at least try, if you got the info that the cleric was preaching this then there must be someone among his followers who doesn't seem to agree with him and thinks he is serious, that would at least make the effort somewhat worthwhile. The case needs an investigation and not just wait and see what happens.

Of course there has to be a believable threat, usually there is a judge to decide such things, just like whether police gets a search warrant etc. If the judges are with the executive in opressing the people then you got worse problems than some slippery slope in your freedom of speech.