The better issue....
When is it right to stifle the speech of others?
A good question and one that has no easy answers. I think most people would accept that there must be some limitations on speech (the classic example being falsely shouting "fire!" in a crowded theater) but where to draw the line gets tricky.
Even if you say that the line is when speech causes harm, it can be difficult to determine what constitutes harm, whether that harm was a result of the speech and what the context and intent of that speech was. A couple of examples here: There have been multiple cases in which people have taken their own life after being harassed, stalked and bullied online. On the flip-side, the British comedy show "The Goodies" killed a man as he laughed so much that it triggered a cardiac arrest.
In the first example, there's clear malice and the desire to make somebody suffer. In the latter example, the opposite is true.
So even speech/expression that results in death can have ambiguities. Going back to what I said earlier, context and intent are crucial when it comes to determining whether or not somebody's speech has gone too far and warrants legal action.*
*For the record, I personally don't believe that simply offending people warrants any sort of legal action. You need to go a hell of a lot further than just being tasteless before I'd consider such a course to be appropriate.