On hate speech and incitement

A lot of people are asking those who discuss Islam as a threat whether or not they feel responsible for the massacre.

First of all, the question is flawed in that considering oneself (partially) responsible is not the same thing as feeling bad about it and thinking "would this have happened if I hadn't said those things?", and it's usually not quite clear which one of those things people are asking about.

But that's not the point. What just happened was, in effect, a hate crime against the Norwegian Labour Party. I have a question to the people who connect the public debate against that party (or similar parties in other countries) with this crime: how careful do you think people should be in their speech? Should one avoid expressing any dislike against a particular party? Should one only avoid incitement to violence? Something in between?