Why does Glenn Beck have to tell his audience to “reject violence”?

In a research item today, Media Matters documented how Glenn Beck -- who regularly engages in violent rhetoric on his Fox News and radio shows -- frequently implores his audience not to engage in violence. Beck's habit of warning against violence raises an important question: Why does he feel this is necessary?

This question is important because there have been at least two incidents of violence against police that have been linked to rhetoric similar to the violent speech Beck engages in. In the most recent case, the shooter reportedly told police he wanted to kill “people of importance at the Tides Foundation” -- a little-known organization Beck has frequently attacked on his Fox News show.

Beck isn't the only major right-wing media figure who pushes extreme, often violent rhetoric, but he is the only one who admonishes his audience against violence.

What does it say about his audience or his violent rhetoric that this is the case?