He talks about working two jobs but this was during Family Ties & Back to the Future, 6 years before his symptoms. He describes sleeping in the car but no mention of illness. At best it's "can't be good can it?" and "confused about which set I was on" but no mention of sickness. Were this to be a cause, and I don't there is any evidence to suggest it is but I feel the doc wishes to insinuate so, it would be a stress/sleep/overwork type risk factor.

I would note the irony that you bemoan people for not believing something when the evidence you cite isn't there - it suggests more caution is required! From my own reading, that sums up the topic: people are open to viral theories but the proof just isn't there yet so believing it is premature. Parkinson's remains poorly understood in both mechanism and cause. It is said to be "a combination of genetic and environmental factors which might include pesticides and head injury". I imagine post-viral consequences could fit within head-injury type risk factors but we are not at a position to make statements of fact about such things.