I think Opt Out Day will be a flop.
The vast majority of the folks who travel on the day before Thanksgiving are the infrequent travelers. I don't think they're going to put up with any shenanigans coming from whining frequent fliers who think they are entitled to special treatment, special exemptions and special seating. For the TSA employees, this is just another work day. They're going to pull their eight hour shifts and then go home. I don't think it really matters to them whether or not someone wants to undergo a body scan or pat-down. At the end of the shift, that TSA employee goes home while some passenger has to deal with a lobby full of angry passengers who were delayed in line, possibly missed their flights, because this idiot wanted to take a stand in protest.
I think the airport police are going to spend more time keeping the angry non-protesters from killing those who decide to "opt-out" in protest.
In the end, nothing is more effective than peer pressure. My bet is that those who say they're going to opt-out in protest will end up chickening out.