Method in their madness
Danish newspaper prints cartoons implying violence/suicide bombing is intrinsic to Islam, arguing a right to do so under freedom of expression. A group of Muslims test their freedom of expression by dressing as suicide bombers and holding placards threatening to kill those responsible for the cartoons. Hypocritical? No. Stupid? No. Enemies of the Muslim community? Yes. Here's why.
To be consistent with the recent trial of Mark Collett and Nick Griffin, the government should try to prosecute these protesters (using existing legislation). But Mill in On Liberty (which I subscribe to) doesn't necessarily agree with government policy - I don't think the BNP had committed a crime whereas the protesters did.
So far as I understand the BNP charges - they were accused of inciting or being reckless to incite racial hatred during private BNP meetings. Mill says that the right to free speech stops with incitement to violence, using the example of a speaker railing against corn merchants outside the property of a corn merchant. Those roused by the speech have a ready target for their frustrations (the corn merchant's house/warehouse) and violence is very likely to result. Nick Griffin did not directly demand violent reprisals (unlike the Muslim protestors) and his speeches were made at private gatherings with no immediate target for the audiences' frustration. Anyone who is not an undercover reporter and attends a BNP meeting is likely to think bad things about ethnic minorities already and is unlikely to be incited to anything they couldn't think up in their own kitchen.
My problem with the Muslim protestors is not that their placards would encourage Muslims to undertake violent attacks. But by publically encouraging Islamophobic stereotypes they were inciting non-Muslims to commit violent acts against Muslims. Violence would probably have erupted outside the Danish Embassy if the protest had not been policed. Attacks against Muslims nationally will doubtless increase as a result of this episode. This was possibly the intent - the theory being that attacks against Muslims drives a wedge between non-Muslims and Muslims and rallies more Muslims to the extremist cause.
The Muslim community is already vocally condemning these lunatics - they should continue to do so and as loudly as possible.