Why would it be a joke? They applaud the slaughter the unborn in real life, why should they refrain from slaughtering the born who oppose them in their fantasies?
This is an excellent illustration of the sinister impulses among many on the Left.
We should do everything we can to make Limbaugh, Sean Hannity, and every conservative blog in the country aware of it. We should also e-mail it to every liberal and "moderate" friend we know. And every conservative, for that matter.