Io9 makes a worthwhile call: Posthumans, Rise Up And Destroy Hollywood!
Why is nearly every depiction of enhanced humans in film deeply negative? The above post catalogues the anti-mutant, anti-cyborg, anti-hybrid and anti-genetic engineering bias of Hollywood (while noting that sf books and comics are far less biased - it is not just a "makes good story bias").
I don't think one can just blame this on liberal bias; the denigration of the posthuman seems to be based on rather bioconservative views that are not tied to a left-right scale. Rather, they deal with perceived transgressions against purity/sanctity, one of the five psychological foundations of morality in Jonathan Haidt's system (the others are
authority/respect, ingroup/loyalty, harm/care, fairness/justice - the violation or following of these tend to be what drives the rest of the plot). Such a bioconservative view is based on the idea of a given natural order, and transgressions against it are inherently immoral.
Of course, buying into this idea means that one also accepts a worldview that has a fixed moral order that conforms at the very least to our (perceived) biology, and quite often a lot of other unstated baggage of who and what is pure, natural and authentic and what is impure, unnatural and artificial. This can be done from a conservative religious perspective or a conservative political one, but just as well from a leftist perspective - just read the claims of purity and ethical goodness on the labelling of any organic product, claimed to be free from transgressive genetics and the forces of modernity.
Cherishing a complex human nature does not mean one has to subscribe to such hierarchical or purist views. But it is much simpler to cleave to the over-simplified view of how the world works than take responsibility not just for one's actions but for attempting to decide what elements and relations in human nature are good and bad. Being a self-creating posthuman means making many difficult judgements with ill-defined consequences. People who like clarity and certainty more than autonomy and empirical experimentation would hence be disposed to a bioconservative view.
On a lighter note, I have just discovered some fun transhumanist themes in the music propaganda of Dr. Steel. Fibonacci is about von Neumann replicators and has a catchy chorus. I guess the theme of Singularity is pretty obvious ("zeros and ones, the curves' begun//nanotechnology transcending biology"). It is an odd fusion of hiphop and mad scientist humor/aesthetics. I may not be a toy soldier, but that is just because I want to take over the world first.