Give three solid facts why this isn't a good idea.
Some preemptive responses:
Conspiratorial drivel about more government control in your life is ridiculous. Get a life.
This makes drivers dumber is a load of bull. Unless you've got x-ray vision, you can't see what a rear-facing camera can see. Unless you do a walk-around every time you back up, you're part of the dumb driving masses too. You're probably the same person who thinks ABS, stability control, AWD, auto headlamps, DRLs, right side rearview mirrors, tire pressure monitoring, and every other safety function also "dumbs down" the driving experience. If this sounds like you: Stop being obtuse.
Yes, today's cars have poor sight lines and rearward visibility. That's also why they do well in crash tests. You want good side impact? You get a high beltline. You want good rollover strength? You get big pillars. This isn't changing, live with it. Again, you don't have x-ray vision.
No, it is not expensive. The camera is the least expensive item in this system. The bulk of the cost is the large screen, full color displays. Now that all but the most base model cars have these displays, implementation of the camera is trivial. By 2018, such displays will even be more ubiquitous, further mitigating costs. Most models today have a camera as an option, so the engineering cost is already baked in. It's just a matter of raw piece price, which will go down as adoption rises.