Even for activist investors, hedge fund manager Dan Loeb is controversial. No one accuses Carl Icahn of playing with kid gloves, but Loeb’s attacks can be particularly vicious and personal. Most people reading this site are probably well aware of Loeb’s high-profile fights with Bill Ackman, Sothebys (NYSE:BID)’s CEO William Ruprecht and others, but William Cohan’s takedown piece in Vanity Fair is still a fun read just for the amount of dirt he convinces Loeb’s former friends and colleagues to spill (much of it anonymously). Dan Loeb’s letters “I think he’s got a bit of a Napoleonic thing. And I think…