Dangerous thoughtlessness and free speech

The statement of the day is from Juan Cole about the draw Muhammad Day:

I think when you know people have died in violence over some piece of thoughtlessness, it is the height of irresponsibility to repeat it for no good reason.

I agree with Cole's sentiment, but disagrees with his conclusion. It's always better to live i a society where thoughtlessness, even when it is bigoted and can produce violence, can be expressed because it reminds us that the civility and the education necessary to maintain a liberal and open society are never a given