It's also important to separate psychological addiction (which is basically what is being discussed) from physical addiction. Physical addiction is when you experience withdrawal symptoms when the substance is withheld. I am physically addicted to caffeine because I get irritable and headaches when I haven't had my coffee. I am not physically addicted to nicotine because I have not vaped for days at a time and experienced no ill effects. Physical addiction + harmful substance = problem. Psychological addiction is much harder to quantify; I am far more concerned with avoiding harmful substances that cause physical addiction than with trying to determine if I have an "addictive personality."
As far as harm from vaping PG, it would be wrong to say definitively that there is zero harm. Hell, there is harm from drinking too much water! But we do know that PG is safe as used in thousands of everyday products. Thus, any harm from inhaling PG would be respiratory-tract-specific; once it's in our bloodstreams, it's really no different from ingesting it. Based on the scant evidence we do have now and the real world experience of millions of vapers over the last decade or so (give or take), I think the arrow on the safety gauge points more towards the safe side than the harmful side.
As vices go, I see vaping as pretty harmless. Until valid scientific evidence emerges that contradicts that view, I feel pretty safe in continuing to practice this vice. Everything else is just so much noise with an agenda than anything else.