Dj, I also had a terrible experience opting out at DEN. My usual MO is to walk authoritatively through the metal detector and if stopped, to request an opt-out. My request was also met with eye rolling and an attitude problem.
In addition to the eye roller, the person that did the pat down seemed inconvenienced when I requested not to stack a heavy suitcase on top of my Versace sunglasses.
As a person who makes their living off of testing the safety of medical imaging equipment (among other things), that scanner is simply money out of the pockets of people like me. Add that to the potential for negative longterm health effects that are currently not known, I refuse to go through them under any circumstance too. I make that choice every week, but there's no excuse for TSA acting inconvenienced when a passenger exercises their right to opt out.