We two come from different political and philosophical perspectives, but on this we agree...
What two perspectives are those, social paleo-conservatism and newly-minted neo-conservatism? I mean, Alan Dershowitz wrote a book semi-in-favor of judicial torture, for the love of mike. You don't slide much further to the right of that without getting into Franco territory, to slide deeper into Godwin territory myself.
No arguments with the substance of their argument - I'm not too sweet on the supine mainstream press on a good day when they *aren't* bearing the throat to aggrieved violent street-thugs & bearded maniacs. But ad hominem has a value independent of invective - who makes the argument informs the value of the argument in a practical fashion.
A voice testifying against interest is more interesting and more convincing than a person arguing his or her own case, to the benefit of his or her own intellectual trend or inclination. This is why a "hey! this liberal is talking up a conservative argument" or "wow! look at this reactionary attacking this Republican administration" only has impact for the first few iterations for any particular actor before that actor expends his or her "testimony against interest" ad hominem value, and becomes a voice for the side he or she is now habitually supports.
I'm thinking in particular of Roger L. Simon and Christopher Hitchens, who both played the "leftist in support of the war" hand so hard that they're essentially spent as voices of the "left", and probably Pat Buchanan & the Lew Rockwell libertarians for counter-examples thereof on the left, although I don't pay close attention to the leftward version of this phenomenon, and those might not be the best possible examples.
Via Glenn, who bought the "two perspectives" line hook & sinker.