Frankly, you read what they wanted you to read. Not to sound like a conspiracy theorist (which I am not) but the FDA did not have one thing to say about them until the gained oversight on tobacco products. Then all of a sudden they were dangerous with a "scientific" paper that, under scrutiny, proved them to be as dangerous as the FDA approved nicotine patch. That patch has the same carcinogens at the same or higher level than their electronic cigarette liquid report. Yes, they did their study on the liquid directly, not what actually get inhaled.
If you do not actually understand what you are reading, don't trust those who will lose money to interpret the results for you. Since its not FDA regulated like the patch, and its cigarettes themselves, the FDA gets none of the e-cig taxes.