I would take anything from quackwatch with a huge grain of salt. It is very biased against all non-synthetic, non-pharmaceutical medical treatments. The author either willfully ignores the science published on herbal pharmacology and nutritional medicine, or he isn't paying attention, or he has an agenda. In any case, I'd rather get my info on medicine from a more balanced source.

Edit: here's a balanced source on the current research on vitamin C supplements. Scroll down to disease treatment (http://lpi.oregonstate.edu/infocenter/vitamins/vitaminC/)