You finally get it. While it may inconvenience other passengers if someone with a wheelchair shows up at the last minute, that's an inconvenience that they must tolerate. Federal law is intended to make it possible for individuals with a disability to travel without being subject to special burdens, such as requiring them to show up and board earlier than other passengers.
Likewise, if so instructed by the flight crew, you should tolerate the small inconvenience of not eating peanuts onboard, in order to prevent someone with a severe allergy from suffering a reaction and/or dying.
Incidentally - since it's become quite obvious that while you like to pontificate, you don't know much about the actual laws and regulations that apply to travel by passengers with disabilities - DOT rules provide that if a passenger needs assistance in deplaning, it does not need to be provided until all other passengers have left the aircraft. See 73 Fed. Reg. at 27620 (May 13, 2008). Not to mention that you must keep your seat belt buckled until the aircraft has completed any ground movements. See 14 C.F.R. § 121.311(b).