This is bogus! (and I am one of the left-wingers here).
I am chemist. Propylene Glycol IS NOT the same as ethylene glycol (your typical car antifreeze).
It is approved by the FDA for use in food products (and many other things).
This is the Merck Index entry for PROPYLENE GLYCOL: "Taken internally, propylene glycol is harmless, probably because its oxidation yields pyruvic and acetic (occurs naturally when you metabolize sugar) and acetic acid (vinegar)."
This is the Merck Index entry for ETHYLENE GLYCOL: "Constitutes a hazard when ingested; eg. drinking antifreeze fluid. Transient stimulation of CNS followed by depression, vomiting, drowsiness, coma, respritory failure, convulsions. Lethal dose in humans is approx. 100 mL."
I will repeat...There is a big difference between Propylene (cigar humidor 50/50 juice) and Ethylene (car antifreeze) Glycols.
Also, propylene glycol has very little vapor pressure and should never get on your cigars anyway.