When Ann Coulter says that someone should poison a sitting Supreme Court Justice with whom she disagrees
, I don't think saying it was a joke, reduces the responsibility. Killing people isn't funny, not even if they are government officials with whom one disagrees.
As a number of people have found out, no one at airports has a sense of humor when you bring up weapons. As a local man found out, mentioning anthrax in jest can cost you your job and result in criminal charges being filed, even though he had a very valid reason to be sarcastic.
The right wing has a long record of advocating violence against people, and then pretending it was a joke when they are confronted.
This sort of behavior isn't acceptable, even if you are a Republican.