I understand where you get the bias from, don't get me wrong.

There's "coding" (as you put it) in media and TV that people who are stupid, are lower stationed economically, working dead end jobs, living in squalor, etc. The stereotypical image of the idiot during the first section of the film loosely fits a number of those stereotypes, like living in a trailer.

Media and TV have made intelligence almost synonymous with success and financial gains. Certainly that sequence doesn't help. The two "intelligent" people examples are all put together in their upper-middle, or upper-class home and apparel, speaking of their careers and "the market" or whatever. Here are the smart people being very closely aligned with two successful professionals, with plenty of money to live on the more luxurious side of life....

That portrayal is a strong example of the point, whether you want to call it bias or coding or whatever, either the people who created the scene, or the audience watching the scene, have conflated the idiot, with someone who is poor, and intelligent people with those that are wealthy.

But the way it's portrayed, and what you may think it's trying to portray, isn't what the focus is for that scene. If you listen to the narrator, and focus on the literal story telling provided, while the idiot may look "poor" to you, they're not set as an example of someone who is poor, but as someone who is stupid.

Could they have done a better job to ensure the audience doesn't conflate stupid with poor? Probably.

I would argue that if your main take away from the first act of idiocracy, is that it's not about the idiots, but rather has some connotations about the poor, then the idiot in that scene is the observer.