And just to elaborate on this, non-USP PG is used everywhere. If you cook and use flavorings, take a look in your cupboard and check out the ingredients. PG will no doubt be used as a carrier in some of them. Aside from flavorings it's also used in the manufacture of many foods: my grandfather, who works at a cheese house, told me they use it in their process and it no doubt gets into the production.
The nitrosamines are from the nicotine extraction, which again indicates that they were probably not using USP nicotine. The company that produced that particular e-cigarette is now out of business.
The dose makes the poision; analyze everything around you and you may find a very small percentage of unwanted and dangerous chemicals.
Conflating the e-cigarette industry with the tobacco industry is entirely incorrect. The e-cig industry was not started by a tobacco company, and big tobacco has only recently taken interest by buying up companies and starting their own brands.
Also note, that the amount of DEG and nitrosamines were well within acceptable standards enforced by the FDA. The whole media circus around it was very shady.