[shilala]

Cool article, Joe. There's a reason for that, but they really didn't touch on it.
The nicotine is the good part. The rest, not so much.
Nicotine can synthetically open channels that allow control of stuff. That in itself would delay onset of Parkinson's.
Parkinson's and a lot of other neural disorders and acquired. They result (supposedly, and it makes sense) from missense mutations caused by environmental factors, such as poisoning. Poisoning is a relative term. It can be anything, like poisoning from taking too many tylenol for 20 years.
That said, you could also develop Parkinson's from the ammonia in cigarettes, or other associated toxins. The nicotine connection makes sense as to why there's a lower instance. Remove all the other crap, and cigarettes would probably make a big difference.
I'd love to see a study done on cigar smokers and snuff chewers. It'd be interesting.