Franklin is the Frag netrep, so one would expect him to be right, and he is. A dropped weapon card goes onto the playing field. A dropped gadget card is
discarded. You should never have a Gadget or Special card underneath one of the numbered markers.
The Over/Under question is even specifically addressed in the
Frag FAQ -- you discard Over/Under and the two weapons are now unlinked.
Whatever rules lawyer you harassed must have never read the FAQ. One of the things I try to do when running games as a MIB is to bring a printout of the FAQ with me -- I find it useful for situations like the ones mentioned here.