With white supremacists threatening Obama, should Rush Limbaugh really be continuing his racist attacks?

At what point does traditional conservative racism end up inciting violence? With Barack Obama now under Secret Service protection, reportedly after being threated by white supremacists, should Rush Limbaugh really be continuing to mock Obama as a "negro" and more? And should Dick Cheney really be a regular guest on a show that calls African-Americans "negroes"? The BBC has more on the latest hate from Rush Limbaugh.