That's an old chestnut and due to the mis-configuration of 52J planes which causes all sorts of problems.

The correct procedure is to let F pax disembark first by Door 1. Then J pax should be allowed to disembark by Door 2, moving the jet bridge if there's only one. During all that time, the WTP pax are restrained in their cabin and searched for wrappers of food stolen from the Club Kitchen during the flight and the waiting police will arrest where necessary. In extreme cases they can be swabbed down for crumbs of CW cake and suchlike and tested in a spectrometer while the WT pax disembark.