Having said that, I had a slightly critical discussion with altariel about the political favour of the film, for example its use of race, gender, and liberal values.
It is obvious that Joss Whedon sets up tension for emotional payoff (duh) and uses social and genre conventions to do the set up. A common device is to invest power in a conventionally powerless figure, and to put truth in the mouth of a conventionally amoral or stupid character. Obviously writers have been doing this since year 1.
I think Joss Whedon dwells inside middle class liberal America, and therefore the value system which he is using ironically to set up the tension is the value structure of this liberal, fairly well educated audience, and their understanding of genre conventions leading back through liberal critiques of golden age SF and back. A context we all share to some extent.
One potential problem with this is that Joss sets up irony within the context of these shared values - but they aren't universally shared so the show can be seen (and has been) unironically as a crude advocacy of anti-liberal values. So, putting quasi-liberal political talk into the mouth of the oppressive baddies, or making many of the oppressors black, is intended (I am sure) to increase irony and emotional tension, by playing on shared values and genre conventions that we almost take for granted. However, I think the show has played quite differently among groups who read it without this double-layer of irony, as a simple libertarian or even neo-con tract.
A second more serious complaint (similar to the one made by temeres in the link above) is that the the characters, the writers, and the whole damn lot of us, are middle class weeds playing at being tough guys, that they (and we) don't really confront the darkness at the heart of things, and the hopelessness of resisting it. A part of me wanted the film to be the heart of darkness that it wasn't. Liberal middle class irony only goes so far.