What a bunch of rubbish! Honestly! If you washed your hair everyday, you'd soon have hair like hay (unless you put something on it to restore the natural sebum you washed out).
There's nothing wrong with stretching washes. Washing hair once a week isn't bad for it. Stretching longer is fine so long as you keep the hair healthy by brushing or combing it daily..and taking steps to keep it covered when outside (less chance for it to pick up stuff from the air).
By their reasoning, I would have been bald years ago! I wash once a month and have never had any problems.