I have had several people expressing a wish to to get off but have been fortunate in so much that only three or four have actually got off. It's always wiser not to have people who don't want to fly left behind on the ground than have them causing havoc in the air. So you have to just accept the delay and also assure yourself that nothing has been left behind by the leaving pax. It is also fair to point out to them that it may take some while for the their bags to be found, that they'll have to forgo the fare they have paid and may also be charged for the additional costs incurred by the airline. But left them go if persuasion doesn't work. However, if you perform an unscheduled en-route diversion and people wish to get off, again let them but you don't have to give them their bags. As nobody knew there was going to be a diversion the unaccompanied bags represent such a negligible risk that you can depart with them. It's then the passenger's problem to get the bags from the destination.
PM