Comedian Kathy Griffin is getting death threats, as well as cancellation of gigs, from fanatical supporters of the troll, because of a video in which she had an imitation of his severed head.

I don't think things have degenerated to the point where civilized people should reply in kind to the violence and threats of the supporters of the troll. Griffin clearly agrees, and didn't intend to make a threat.

Making a statement that is misunderstood is not something that calls for a humble apology: all humans sometimes speak unclearly, and there is no need to be ashamed of that. It would have been better for Griffin to say she regretted the misunderstanding and would take care to avoid it in the future -- while restating the intended point in some other way that would not be misunderstood.

If you are faced with a wave of hatred from people who are offended for an invalid reason, don't give in to the urge to apologize. The apology harms your reputation in a way that others' threats cannot.