There are plenty of smart and well-meaning conservatives worth listening to, but they tend not to be the ones who call him "Hussein" or knee-jerk criticize Obama just because that's how they make their living.
Rush is first and foremost an entertainer. His politics are becoming outdated by the changing demographics of our society, and so it is not all that surprising that the more he resents the changing dynamic, the more shrill he comes across.
Put it this way: Given these changes, those that buy into the Rush style of politics or thinking are dinosaurs. And they will suffer the same fate.