That's correct. Lack of evidence isn't enough to disprove a theory; what you need is evidence that directly contradicts the theory.
We are approaching the point where the lack of evidence becomes evidence of non-existance. But as of yet, I know of no alternative theory.
There are two projects I think are well suited for this purpose. A CC stripe reader or a SIM card reader. Both are very simple circuits, both require exactly one specialized piece of hardware (the SIM reader or the tape reader--and old cassette player head works fine). Both can provide data to the COM port to any computer, and need only very simple software to manipulate.
The problem with starting out with asm or C is that it requires you to talk about the machine. You need to lecture on the differences between the heap and stack, passing by value and reference, and with asm you need the segment and instruction explained before you can let them loose.
To introduce general programming, I'd suggest either Prolog or Scheme. Prolog may be the simplest to begin with, as it teaches variables, logic and flow control. Scheme increases the difficulty with flow control and looping.
I also second the suggestion for Lego Mindstorms as that gives a physical response to writing a program, but that may be too expensive for you course.
This article on news @ nature.com discusses a recent discovery of a technique that removes the need for eggs or embryos. Three different groups in the past week have reported research that normal skin cells can be reprogrammed into an embryonic state in mice. The race is on to apply the same procedure to human cells. From the article;
The solution of problems is the most characteristic and peculiar sort of voluntary thinking. -- William James
