Michael Barone's cocoon: Just for liberals?

Michael Barone says that liberals only listen to liberal arguments, but conservatives have a more varied diet of ideas because they're forced to be exposed to liberal media culture. The result is that liberals only know how to preach to the choir.

Liberals can protect themselves better against assaults from outside their cocoon. They can stay out of megachurches and make sure their remote controls never click on Fox News. They can stay off the AM radio dial so they will never hear Rush Limbaugh. 

The problem is that this leaves them unprepared to make the best case for their side in public debate. They are too often not aware of holes in arguments that sound plausible when bandied between confreres entirely disposed to agree.

I'm not sure that liberals are uniquely vulnerable to the malady of ideological isolation. Conor Friedersdorf notes the topics that dominate conservative media these days:

In addition to taxes and spending, the rank and file currently spends a lot of time obsessing over trivial nonsense: for example, an imaginary race war against white people; The New Black Panther Party; and a liberal schoolteacher abusing her position somewhere in America. Those are but three stories in conservative news right now, alongside the constant obsessions with liberal media bias, anything involving "God, guns, and gays," statements by Janeane Garofalo-style celebrities, and ginned-up kerfuffles we can't even presently imagine.

 I'm not sure this really helps conservatives make better arguments than liberals, but if Barone wants to think so, perhaps he's indulging in a little cocooning himself.