This is the most frightening part of the current political landscape.
We need to recognize, as a country, that there is exactly one requirement of terrorism: threatening or enacting violence as a means to enforce your political will on others.
You don't need to have a particular skin color.
The ideology you want to enforce doesn't have to come from any one particular book.
You don't need to be a part of an official "terrorist organization".
You don't need to actually kill anybody.
It's a simple rule of thumb; I bet even Rush Limbaugh can wrap his mind around it.
If you, as a political statement, do something that
a) might cause something to explode or crash into something else, or
b) might kill somebody,
YOU ARE A TERRORIST.
It doesn't matter why you're doing it. People who do this because their political party has lost power are terrorists. People who do it because their political party will protect them are terrorists (but generally fall under "corrupt governments"). People who do it because it is "moral" to kill people who disagree with them are terrorists. People who do it because they feel a foreign power is exercising too much control over their country are terrorists. People who do it because someone on the television tells them this sort of reaction is "expected", normal, or acceptable are terrorists. And the people who tell them this sort of behavior is expected, normal, or acceptable are terrorists.
The reason this makes me really frightened is because trying to apply this simple definition makes it seem like an awful lot of the right-wing pundits and quite a lot of their leadership are terrorists.
Harsh? Find a clip of some pundit talking about how some liberal political decision will lead to violence, and ask yourself: would a normal, healthy human being respond to such a suggestion with anything other than barely-concealed horror? What about a terrorist, who wants to see his enemies killed rather than allowing them any advance in their agenda? Which of these imaginary people is the pundit acting more like? A person capable of feeling empathy for their fellow humans, or a terrorist?
EDIT: Apparently, this is being investigated as an "attempted threat".
Which it is not. I don't even know what an "attempted threat" is.
It is attempted assassination of a U.S. government official.
As long as you refuse to call it that, you are ignoring the problem. Until you drag the people encouraging this violence before a goddamned grand jury, you are refusing to confront this problem.