The dangerous chemicals are a reality if you vape at insanely high temps. If you do the research you find that diacetyl and other bad things that could be produced generally occur at temps we don't reach unless we vape on a dry wick. Yuck!
Keep it reasonable at a level that recreates that of a standard cigarette, keep your wick from going dry, and the bad chemicals aren't produced. It's why I try to stay at 3.7v and 1.8 ohms. That gives me a cigarette like experience with good flavor. It's the push to high watts that is more likely to produce the bad stuff if the wick isn't able to keep up. Anything with a dry wick will heat up and begin to produce new chemicals. Don't let that happen.
It's just my belief, but I don't really think the bad chemicals are produced within reasonable
vaping ranges. Coming down hard on ecigs because they can be abused or used improperly is like outlawing automobiles because people can create unsafe conditions by driving recklessly and exceeding speed limits.
This study has graphs showing the output of ecigs and comparisons to EPA guidelines for daily exposure. If you get bored with reading the whole report, at least look at the test results and the charts that compares vaping exhale to EPA standards for clean air. We beat them all by a significant margin. That starts on page 15 and continues on a few pages.
http://publichealth.drexel.edu/~/media/files/publichealth/ms08.pdf