Hm, no. The dumb people have already judged the lot for the worse. They don't understand logic reasoning.
No muslim need need to say anything. Just cause I'm white I'm not going to condemn openly or give any excuse to anyone when a black man gets murdered by "one of us". Even if there's any racism involved.
The bold part is where you´re wrong. It´s not a racial issue and it´s also not comparable to "common" crime. Terrorism and the demand for special treatment at the cost of others (which is what the whole Mohamed cartoon incident is) is a completely different matter than your run-off-the-mill robbery.
Since these Muslim extremists say they defend "the faith" and act in the interests of their fellow Muslims, they become spokesmen for the moderate ones. And that´s a grave issue, since the moderate Muslims surely wouldn´t want to be represented by these extremist lunatics.
So usually, when you don´t want to be represented by someone you distance yourself from these people in order to...well, not get confused as one of their kind.
A better example would be radical leftists, burning private property, injuring policemen and bystanders. Any sane and moderate social-democrat would want to distance himself from these extremists. Incidently this also is standard behaviour, because they don´t want people to think they get represented by extremists and support them in their cause.
That´s why the whole silence from the "moderate" community is rather strange. For example, there´s barely any uproar from spiritual leaders when there are incidents that infringe our rights or disgusting acts that are conducted in the "name of Islam". I see silence as either indifference or silent approval and I don´t know which is worst.