I don't like AUs for a lot of reasons, but I think the chief one has to do with one of the reasons I don't like porn fic. About ten years ago, I was of the theory that fans wrote porn when the actual material didn't sufficiently capture their interest -- ie, if you really liked THE X-FILES, you wouldn't be writing dumb porn about Scully doing Mulder, you'd be writing casefic in an attempt to emulate the actual show. I don't know if that was true then, but it certainly isn't true now; for a lot of people, porn is the entire point of fandom. But AUs often give me that feeling: if you like these characters so much, why are you putting them in weird scenarios where they're so far removed from what made you fond of them in the first place?
And putting existing characters and dynamics into an AU often is clumsy as hell. Consider mine -- I like the idea of Varro as the guy who won't leave you alone at work, the guy who steals his buddy's coffee cup, but my god, the shit that comes out of his mouth, and Crixus's in that scene. It's the most hostile work environment imaginable. Especially since there's not a scene with Lucretia and Ilythia in Lucretia's big-ass office where they're talking about the employees as pieces of meat. There's a fine line between characters saying appalling things that you laugh at (see: everything that comes out of Crixus's mouth, on the actual show) and characters saying appalling things that make you go, "Whoa. Dude."
For me, I think it's the lines about "intern pussy" that do it. Not that you can't laugh at it, but I think it could have been a hell of a lot softer and kept the funny without being so off-putting for potential readers. If they'd just said "interns," it wouldn't have nearly been as bad. I think even if I'd taken it a step back and tried to make it sound more archaic in flavor -- "the rule when you tup an intern's cunt" or something -- it wouldn't be as offputting, or feel as misogynist as it does in the version as it stands. The more familiar things look and sound, the more we put them into familiar emotional context; one reason that it's possible for SPARTACUS to be as batshit as it is is that it's set in a very *unfamiliar* world and emotional context. The dynamics are all different from the things we're used to, so we're willing to like characters we would ordinarily find repugnant. (Barca, for example, *murdered a child.* And yet he was one of the show's lights.) But these guys in a modern office saying these things in words we're used to hits buttons surprisingly hard, so if you move this back into an office setting, you really have to ratchet back to keep the dynamic from being horrifying. I didn't ratchet it back nearly enough, so it comes off like SPARTACUS by way of Neil LaBute.
And then there's the little stuff. Like Varro's bit about interns being like whores. Well, wait, whores are all over the place in SPARTACUS; does that mean that prostitution is legal and widespread in this officeverse? What kind of place is this? It's modern, clearly, because it's got computers and Al Gore and such; what the hell is going on here? Basically, I dumped a bunch of characters into a setting that doesn't fit them, and didn't make any sense out of it. That's a badfic AU for you: it's the fanfic equivalent of an SNL skit. Nothing happens, and the funny isn't really worth it.
I do really like the running gag with Spartacus's coffee cup, though. That's funny.