The basic crux of the issue for me is this: you can control a society via the flow of information through that society. Both reading and more recently, programming are activities intimately connected to the flow of information through modern society. Along with an understanding of programming comes a greater understanding of computers to computer networks to privacy issues and all manner of things that more people should be thinking about more conciously, regardless of whether they wish to program as a career.
While no doubt the flow of material through plumbing pipes is also quite important for societies in general, I don't think an understanding of plumbing affords quite the same insights and protections against being potentially manipulated by the powers that be as one might acquire through the pursuit of reading and programming.