There are many comments supporting these guys.
The complicating thing tends to be women's fashion - it seems churlish to say that women cannot wear shoes which are largely "open" on an aircraft, as they are routinely worn as part of high class fashion. Yet once you make that concession, it seems hard to tell slob men that no, thongs or sandals are not appropriate. Couldn't the airlines at least go with "no thongs, under any circumstances"?
But the reason I am like David (always wear long pants and shoes and socks on flights - although I will go short sleeve shirt, especially on a short flight) is that I imagine it giving me the best protection from fire in the even of a crash.
You may laugh, but the comments of some aircraft accident investigator I read in (I think) some science magazine (maybe Discover?) years ago stuck with me - he claimed that surviving a crash did seem to be strongly correlated with "paying attention to what you would do if there is a crash". So, people who actually do things like think about their nearest exit and how many rows they would count before knowing they were at it really did seem to have the better chance of surviving.
Wearing cotton, which can stand a lot of heat, to cover most of my skin, seems the least I can do.