The switch is not a MEL, it is not a flight safety issue and thus no reason to delay the flight for repairs. Delaying maintenance to the next downtime for the aircraft, especially a major hub, is common for these sorts of minor faults which need not be operational.

Offloading oneself is absolutely crazy, but people do crazy things all the time and carriers accoomodate them because it is better to deal with on the ground than with somebody who goes off the rails at FL35.

All electrical systems can be shut down in an emergency. The cockpit has circuit breaker access for just that. But, this was not an emergency.