As a disabled passenger I've been told on a number of occaisions by CC that in the event of an incident I should stay in my seat until everyone else is off the aircraft, something that I pointed out that I had no intention of doing as my disability only affects me for walking long distances, not crawling through smoke, climbing out of overwing exits and the like (having done both in connection with work). When travelling on business I get sick and tired of being asked where my 'carer' is and generally being treated with much less respect than everyone else who has paid just the same for their tickets.
People who require assistance during the flight should be located with those who can provide that asssiatance, but those of us that don't shouldn't have to jump through hoops to convice people that we have the ability to look after ourselves. At least I don't have to get a certificate from my doctor that I don't 'give offence' to other passengers anymore.
Flying from Amsterdam to Moscow with KLM I was allocated a seat by the overwing exit and (quite rightly) asked to relocate (politely for a change) by the CC. All well and good so far until I and my partner were replaced by an elderly Russian couple who spoke none of the languages spoken by any of the CC!
Interesting to note that rules regarding who can sit where aren't applied to other factors that would affect survivability such as bariatric flyers, the very tired, those who have been drinking but aren't drunk enough to offload etc. I have friends and colleagues who, although technically disabled, are some of the fittest people I've met and work day to day in high physicality, high risk environments including operational front-line firefighting and law enforcement and would much rather have them by an exit than a corpulent late-middle aged 'able-bodied' person. The one-size-fits-all approach belongs to the last century.