Finn is asked by Organa and the resistance to provide detailed descriptions of conditioning programs TFO utilizes because it is needed for propaganda against the First Order. Finn, tension-filled and on the brink of flashbacks, gives as much detail as he can. When he can't, he decides to give them a way to view archived footage of his stay.
Cue somehow the footage being shown to the entire resistance, with Rey and Poe seeing first-hand what he went through.
BONUS:
Finn discovers people viewing it and tries to pass it off as if it was nothing, just making it even more fucked up.
If conditioning included forced self-deprecating statements by newbies. I can imagine the horror of Rey and Poe having to listen to Finn saying terrible things about himself.
Finn/Poe & Rey; Reactions to Stormtroop Conditioning Footage
Cue somehow the footage being shown to the entire resistance, with Rey and Poe seeing first-hand what he went through.
BONUS:
Finn discovers people viewing it and tries to pass it off as if it was nothing, just making it even more fucked up.
If conditioning included forced self-deprecating statements by newbies. I can imagine the horror of Rey and Poe having to listen to Finn saying terrible things about himself.