In light of my post on politics and personal perspective yesterday, I thought this "exchange" between Mark Levin and Conor Friedersdorf would be of note. Also see Rod Dreher on the controversy. In any case, here you have a case where the principals agree on the broad political issues at stake, and many of the specifics as well,

but disagreemants over style lead Levin to takfir his critics.

In fact, if you read the comments at the first link it's clear that Friedersdorf's point is basically unintelligible to many fans of Levin.