Why is this brought out in such a dismissing and ironic way? He claimed that there may be some treatments with Vitamin C, not that if you take a little a day you'll be immortal. Hell, there are so many different types of cancer, that even if megadosing C helped with one it probably wouldn't help with all.
He lived to his 90s. At that point it was either cancer or heart disease that kills people. That fact that he lived to 93 is pretty impressive in itself.
As someone who recently went on Vitamin D supplements due to low D in my bloodstream, I find it incredibly interesting how medicine is always changing. This knee-jerk skeptic idea about how everything but the current accepted status quo is "quackery" and mocking guys like Pauling is reprehensible. Just a few years ago, no one was checking Vitamin D levels. Now my depression and lethargy have been turned way down as my Vitamin D increases.
Hell, I remember being a teen with ulcers and being told to lay off the spicy foods. I tried to explain to the doctor that I never eat that and he shrugged and wrote me a script for Zantac, it being prescription-only at the time. A few years later H. pylori's role in ulcer creation was revealed and now the standard treatment isn't large doses of zantac, but two weeks of amoxicillin. My ulcers magically went away after that treatment.
Medicine is one of things that moves fast and the jury is still out on a lot of marginalized treatments, concepts, and research. I wouldn't be surprised if Pauling's research eventually fleshed out into some kind of cancer treatment, or at least as a supplemental treatment.