Paul Kinsey is Sterling-Cooper's resident liberal intellectual, considerably to the left of his mostly Republican colleagues in his politics--making favorable reference to Karl Marx, participating in voter registration drives in the South.
Kinsey generally comes off as a prat, which seems unexceptional with this crowd, but it's notable that his prattishness is distinguished by its pretentiousness, down to the beard-and-pipe image he assumes in the course of the series. It is also the case that much of what he says and does is intended to impress women, while he uses the women he is with to impress his male acquaintances. (That he blew his chances with Joan because he couldn't shut up about their relationship pretty much says it all.) It's notable, too, that he got left behind when the main cast decided to strike off on their own and start a new agency.
In that he comes off as yet another anti-intellectual, anti-liberal caricature, and a reminder that Mad Men would not be so lavishly praised were its outlook not so deeply conventional.
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